Probably a few of them, but I'm guessing some other company with a similar business model would have come along with VC backing and eaten their lunch (sure, that company might then be in the exact same place as the current over-valued late stage companies).
Damned if you do, damned if you don't?
[0] http://blogs.wsj.com/digits/2010/07/14/accel-invests-60-mill...
With regards to the second point, as long as as potential outcome of the VC method can bring about some EV of $1B, then there will be someone willing to spend $999M to capture that market.
The problem isn't with early VC money. Dropbox's early backers would have still made a gigantic return on Dropbox setting at a $1bn valuation.
Really, it's not even a problem with their series B ($250M at $4bn). $4bn is a reasonable eventual valuation for Dropbox.
The problem is that they didn't stop there. They raised another $850M in 2014 (in two rounds), which was basically sold on the promise of it being necessary to "win" the storage wars and acquire a monopoly.
By 2014, Dropbox was already a stable company with hundreds of millions in revenue. The only reason to raise money was to shoot for hitting Google/Facebook status (owning a lucrative monopoly). If they had instead accepted that their eventual outcome was a $3-5bn software company, everyone could have won: employees, investors, founders, etc. (Atlassian is an example of a company which did eventually raise substantial VC, but instead of gunning for a monopoly IPOed at a $4bn valuation.)
The problem is that founders ultimately have huge egos and want to be the next Mark Zuckerberg or Larry Page: commanding monopolies so lucrative that they can spend billions on zero-return "cool nerd shit."
So it makes sense why companies would want to stay private if someone is willing to give them the cash they think they need. Problem is, those investors also want to make a huge return, so a 20B valuation is going to come with some nasty liquidation preferences/ratchets etc. to protect the money.
Can't you just raise money at a lower valuation (the dreaded down-round)? You might lose the employees who bought options at the unicorn valuation, but it wouldn't necessarily kill your business.
Why do you need more people when you grow past a certain size? At Drop box's scale they surely must manage their backend at scale and not have people babysit servers. If DBX are using Amazon's S3 for storage then that's one less massive headache to take care of.
Just for comparison, Instagram had 13 employees when they sold to FBK and they sure had scale at that point.
I like a lifestyle business, however if you can clearly go for a $10B instead of $30M while spending the same 10 hours at work and surrounding yourself with 10 times the amount of smart people, then why not.