Earlier quoted context omitted.
Chrome makes it pretty difficult to sideload extensions, so I'm not sure what you're seeing.
Well I’m usually browsing for development tools & such and some of them are advertised as an out of store downloads (which would be preferable as I prefer Chromium). You did prompt be to check how hard it is though, so allow me to get back to you in a few ;) Edit: I didn’t go through manual process but based on this (rather recent) Adblock guide [1] it’s not very hard. Of course one could argue that “developer mode”…
Chrome is unfortunately limited here by the security of the OS. No popular desktop OSes have application isolation: all apps have the same permissions. Any app can write to any other apps' storage.
This means that if Chrome makes sideloading too difficult, developers will just tell users to run their native code which will hack into Chrome, making even understanding what extensions users have or uninstalling them impossible. Sideloading on desktop OSes has to be hard enough to discourage most users but easy enough that developers like adblock don't start looking for an even bigger hammer.
This is what I meant by delicate balance of incentives.
More info here: https://news.ycombinator.com/item?id=4954915