git has more or less completly taken over the mindshare from all other version control system.
This doesn't matter: hg/Mercurial has to be 500% better than git to be able to replace it.
Look at the past changes: they've all been huge shifts in how we do version control, not minor improvements
The DVCSs were 500% better than Subversion (wow, distributed!)
Subversion was 500% better than CVS (wow, renames work! Branching is easy! http support!)
CVS was 500% better than RCS (wow, we can check out files concurrently)
when svn first came out (and up until a few years ago) branching was definitely not easy!
Before this, merging branches was a huge pain, because you had to manually keep track of the commits that needed to be merged.
http://www.minidisc.org/econ113-paper.htm
A technology needs to be 10x better than a previous one for widespread adoption. It has successfully explained many failed technologies and products.
A hypothesis about failure, on the other hand, has to account for the failures and successes. This one doesn't. While it can plausibly explain failed technologies and products, it doesn't explain the historic success of junk that is worse than its predecessors.
A technology can be hyped into widespread adoption. It can be dumped on the market for widespread adoption. It can ride on top of cheap hardware for widespread adoption. It can be bundled with something else, achieving widespread adoption. A technology can be falsely evaluated as 10X better by a large number of complete idiots, resulting in widespread adoption among idiots, resulting in pressure for non-idiots to adopt.
All these effects can overcome the barrier of having to be actually, objectively 10X better. The "10X better adoption barrier" is only faced by honestly promoted technologies whose campaign consists of "try this because it's better for these objective reasons".
With the ultimate irony that people largely use it in a centralized fashion.
DNS is distributed, yet it has a "root" servers.
Even if there a master repository in a given git scenario, it is still distributed because developers have their own repositories, which are independent, and contain a replica of the copies of the upstream objects.
The Linux kernel is a proper example of distributed workflow.
Even if you consider the SPOF-y nature of something like GitHub, more savvy git users will realize that if GitHub was down for an extended period of time, they could push their repo somewhere else that's public, like Bitbucket, or their own server, and keep working and allowing other people to collaborate. And for shorter downtime of the central server (where you might feel like setting up an alternate is too much effort), everyone can still get work done, they just can't collaborate as effectively until things are restored.
The amount of force required to move an object at rest is greater than the amount of force required to maintain it already moving (or something like that).
If you're going to attract new contributors to a system, having the toolset that everyone else uses is a huge win.
I've been at this long enough to have learned (somewhat) each of RCS, CVS, SVN hg, and git. In the beginning there were (mostly) just two: RCS and SCCS, and nobody used SCCS. With time, I've touched several others, had to wrap my head around them, as additional challenges to getting my primary job done, which generally involved solving problems in other domains (or learning other tool).
And ... some of that's knowledge which has stuck, some isn't. The time invested in learning is sunk cost, though there's the problem that it all leaves traces on your brain.
This is something that 20-somethings don't get: it's not learning things so much as unlearning. It's one thing to launch into a field with the hot new technology under your belt. I landed with some awarness of Unix when that was fairly unusual, and parlayed that and a set of tools for 25 years. During which I've not stood still...
... but the rate at which new tools are introduced, and having to sort out which actually will win is a considerable overhead. After a while it ... just gets kind of old. Especially since you realize that all of it is a constructed complexity, largely arbitrary.
How many operating systems (7, not counting Unix variants), shells (9), editors (10+), scripting languages (8), database implementations (7), firewall systems (4), webservers / application engines (6), mailservers (6), document markup languages (6+), etc., etc., etc., do you want to learn over your lifetime? Some are pretty cool. Others ... are just makework.
This spills over to larger highly integrated stuff which previous experience shows is almost always going to be a massive clusterfuck, of which I'll not mention systemd by name.
Which means you want to consider what projects you work on, where you work, etc. Google have a challenge in this regard with their NIH model -- work at Google long enough and you'll learn some really cool, advanced technology. Which nobody, anywhere else, uses. And, no, they're not the only ones. But they definitely come to mind.
Been in the industry since the late 80's. Eventually one gets tired of listening to every single fad.
On the rare cases syntax does change people raise holy hell. It can kill tools. Especially if done more than once.
GUIs have none of these features and change capriciously.This tends to keep user proficiency at a low general level over time.
Web apps only extend this.
One of the most important parts of my job as a sysadmin is the immediate sniff test on trendy technology of the week and being able to spot the obvious pain points early. Bitter experience, it's useful!
(TODO: pointy-clicky interface to systemd)
The last few weeks, after using git for a decade now I guess, I had to use CVS to checkout and contribute some changes to a project still using CVS. Wow, was that painful! One does get used to the simplicty and features of git, and going backward to older tools makes one really appreciate what they give you.
[1] ... in that it provides not just safe mutable history, but shared mutable history.
I use github as a backend, so I tend to do branch manipulation using the github UI, so this isn't an issue for me.
Everything else Just Works. Highly recommended.