I think there are a couple of reasons for this. The raising sallary cap will make draftpicks more valuable, because you can get rotation players for cheap which allows you to spend tons of money for the stars. Teams are therefore more cautious about giving up on picks which are usually assets included in a trade. Players are also going to look for a big payday, which means trading for Players who will become RFA or UFA or have a player option is less attractive because there is a smaller chance on keeping that player on a decent contract going forward. In addition, I think a lot of teams do realise that lateral moves will not make them beat the Warriors/Spurs/Cavs or help them outtank Philly.