They don't want to draw away the focus and attention of the BLM/Police Reform movement by distracting the masses with America's New Favorite pasttime - Basketball.
Instead of being organized out in the streets demanding change, the masses will be huddled back around TV's watching NBA games.
Instead of visible and vocal players using their platform to help organize and lead, they will be sequestered away training for and playing basketball for the next 2 months.
This is a very important time for this movement, as actual things are already in motion that will hopefully make real and lasting change. We do not want to change the subject or provide distractions from the task at hand. We all want our NBA back, but considering the league is 85% black, I'm sure this issue is far more important to the majority of players, considering they still got plenty of money to ride it out till next season starts. I know there were a few teams that were championship hopeful, and they may want their shot at the top, but I'm sure they would never vocalize that desire of the current issues in the streets and the desire world wide for change.
and even thought they plan to isolate and test everyone, it must be noted that the virus is on the rise in all the early open states such as FL, as they never properly closed down to begin with, and nationwide testing efforts never actually happened in any organized and mandatory way to properly utilize the shut down SIP period.
I'm sure many of them would rather "stay home" with family and friends, than to risk it all so the league can get it's ratings.