Seems like this has been skewed particularly by OKC, who was in a very unique situation where they held a lot of leverage over the Clippers, who absolutely had to get Paul George to sign Kawhi, and whose only meaningful assets to get him were future first round picks. They were in a similar position, albeit to a lesser extent (Houston really wanted to do get another star and dump Chris Paul), when they moved Russell to the Rockets.
The Lakers to a lesser extent, were were compelled to trade for AD so that they wouldn't waste Year 2 of the LBJ Plan. They figured there was more competition than in fact there was, and probably could have paid less in picks. But as a FA destination, draft picks will always hold less value for them than for most other teams.
So while I agree with the first two reasons you site, I would say a 3rd reason is because shorter contracts of big stars, and player demanded movement to team up with them, has created greater liquidity in future 1st round picks in order to grease these transactional wheels.