If you have your prices maxed and you promote, how exactly do you expect to earn more in ticket revenue? You will get a bump in TV money and perhaps more in merch, but you don't get more money for having the same maxed prices in the same tiny arena. Promotion brings with it an increase in fan base. If you don't have seats for more butts, you stand to lose a lot of cash.
In lower levels, managing games shape, enthusiasm, and tactics can help you win just as much as having better players. Building your arena is the single most important facet of this game for the young team. A team with a 5000 seat arena will find it very difficult to compete financially with a team with a 10000 seat arena in the long run.
Once I scored a basket that still makes me laugh.