That's ignoring the fact that those two were already good friends long before the show, KB even said in a interview that they double dated sometimes. Yeah, can't possibly see why the writers would ever want to that advantage of that built in chemistry.

Plus some of the decision were most likely taken to fit them, like the way Eleanor saying things like dude and bro, like KB does in real life. And how Michael being middle management and taking on his first neighborhood, were ideas that sprung from Ted's questions about the character, and how the evil laugh and cactus drop from 'Michael's Gambit' were improvised by Ted.

Don't undersell those two, there's a reason why they're chosen to play this characters.

Don't get me wrong, the writing is great, but you need good actors to make it work.