I'm not drunk, "retarded", or mentally unstable

Its a pretty simple calculus: If you don't use it you lose it. But there's a corollary: If you don't try it you can't possibly gain it. For example, if you use an AFO to walk during the early days after stroke, you'll not easily not use the thing again. 

And if I choose not to play violin- an instrument I've never played- I'll not get better at violin. So, both learning for anyone and relearning after stroke involves taking your brain (where learning happens) out of your brain's comfort zone.

Which leads me to spouses. I've met a ton of 'em. The wife is aphasic, the husband loves her, knows what she's trying to say and finishes the sentence for her. (When its men I always get the feeling they're saying to themselves, "Finally, I get to do the talking!") The spouse can become the exact thing they don't need. 

I always liked talking to folks who are aphasic. I usually get trampled by conversations because I'm slow in the think department. Aphasic folks give me a chance to ruminate a bit. Try it. Slow the conversation.

But "I've gotta get on with my life. How is it good to have my wife talk slowly when we're trying to check out (or ask directions, or talk to the gas station attendant)?"

Here's how its good. Do you know anyone who doesn't stumble and bumble their way through conversations? OK, a few people are so verbally dexterous that they don't really have this problem, ever. But nobody likes those people.

Why shouldn't someone who has a language deficit struggle as much as we do? They should struggle. Once they don't struggle, you know whats that's called?

A plateau. 
Beside, aphasia can be fetching.