For me, uninstall means uninstall everything. If I want to stop using a plugin but keep the data for possible later use, I'll deactivate.

I came across a situation where I used version 1.x of some plugin, then uninstalled. Then later, I installed version 2.x of that plugin, and you guessed it, it didn't work properly, because the orphan 1.x data threw a wrench. You can see where a table cleanup after uninstall would have been helpful here.

Ideally, there should be 3 levels of uninstalling/deactivating:
1. plugin not active, but files + data are kept
2. files are removed, data is kept
3. files + data are all removed

However that might confuse the "common" user, so I personally think the best alternative is to have 1 + 3 only (and those are the options that my plugins have). Additional confirmation screens or options will just confuse people more, so I do think there should be a standard.