11 out of 30 NBA teams had 100% home game attendance last season. 18 teams were above 95%. There's not that much margin for improvement there.
http://www.espn.com/nba/attendance/_/year/2019/sort/homePct
Edit: I can't find the numbers for courtside attendance, but it's possible that ticket income for the teams at the bottom of that list is either lower or higher than the overall % suggests, depending on how in-demand the highest priced tickets are.