Why? It's a feature which takes a large amount of work to implement, has a series of poor tradeoffs, won't actually increase the size of the user base much, is incredibly hard to do well and is very hard to market to users. Not to mention the fact that a large number of GNU/Linux distros are aimed at markets where such user land improvements are largely immaterial (e.g. on servers).
The simple fact is that most users don't care about privacy in the same sense that DDG cares about privacy. If they did, then there would be a huge economic incentive for everyone to make these sorts of changes.
The thing to realize is that you can use any kind of desktop environment on any of the main distros. With Ubuntu, moving from its default DE can sometimes result in certain hiccups. Other distros are more DE-modular; that's the feeling I get when working on a Debian desktop, at least.
Overall, Debian is a very user-friendly system (or rather, it exposes the same kinds of interfaces as Ubuntu does, once the leaky UI abstractions in Ubuntu do start leaking. ;)
You're fine for a year or so, but when a new version of Mint comes, if you want to upgrade, you'd need to reinstall everything.
Unless you want to make a statement, then changing the distro might be the gesture you want.
(I thought the malware component might be in a lower level of the OS than the DE)
sudo aptitude remove unity-lens-shopping