So rehabilitation's completely out the window then? Why take an offender and create a situation for them in which they'll be more likely to re-offend and work more closely with other criminals?

I know that personally if my vote was taken away, for example, that I'd lose a great deal of respect for and connection to the state; the meaning and validity of laws would be seriously diminished.

Yeah, that's the whole point. If you make it so a felon is essentially completely shut out from mainstream society, it will be really hard for them to not commit crime again, since they may not even be able to get a job or find a place to live. So in effect you just incentivize them being jailed again, which is bad for them and for all of society, since we have to pay for it.

Lots of felonies are completely ridiculous and cater to special interests, such as felony copyright infringement.