To sum it up:
1. Having to listen to Nike & Money.
2. Listening to the fanbase & season ticket holders (or not)
3. Wanting to do something different and not deal with the weight of tradition, nostalgia, etc.
4. Good/Bad team marketing departments.
To further elaborate, the NBA is an athletic entertainment business and each team has their fans worldwide. The money is always the factor but not the only one. We also have to keep in mind that some teams' have good marketing departments and others... don't. For example, take the Miami Heat. They said that their current color scheme (Red, white, black, yellow) are not changing in the near future yet for the fourth year in the row, their Vice Jerseys are the talk of the town (for better or worst, for the right or wrong reasons, etc.)., When they first made the Vice Jerseys, they paid attention to not only their history but also the immediate market that they're in which is South Florida.
Some teams really do pay attention to their markets the best way possible (Memphis is another excellent example so far 2/3 of their City uniforms were not brand colors at all but every design has paid attention to the local history; Brooklyn Nets and their Local Artists Uni's, Utah Jazz and their jerseys, Portland Trailblazers, Chicago Bulls, hell even the Lakers and their Lore series along with the... Clippers' and their past few City jerseys)
Some teams don't care but money is being printed (New York, but the fireman jersey was their best City jersey and their current one is a collab with a local fashion house, Detroit, Dallas, Orlando, etc.)
Other teams (or every team) has a hit or miss marketing department.
I'll stop rambling on...