Why do NBA teams play undermanned?

I'm watching Celtics vs. Raptors tonight and the Celtics have all of 9 players.

Don't NBA teams have farm teams or practise squads or whatever they could call up players from?

Why do NBA teams play undermanned?nba draft order

have 3 spots they can put inactive and 15 roster spots with 12 active and the option for 10 day contracts or to call someone up from the D-league

but to make room the teams would have to waive a player on salary and teams don't won't to pay a cut player and then have to sign a guy for any short term problem

9 players isn't that bad of a rotation

a lot of top teams over the years only used a 7 or 8 man rotation for the entire season