Reasons for doing it:

Suns- This is an obvious move for the Suns, they need desperate help and they get a great player (most of the time) in Jimmy Butler. They get rid of Bradley Beal who they really don't want anymore, and their only trade able FRP, but it's worth it.

Heat- The Heat have made it clear that they do not want Bradley Beal back in a trade, so instead of him they get 3 good rotational pieces who can help them compete right now.

Pistons- The Pistons are only doing this for that very valuable FRP. They would most likely try and start shopping Beal right away and try and get more assets for him. This move would likely cause them to fall out of the play-in, but that isn't necessarily a bad thing with how stacked this draft class is.