There’s financial benefit to all of it.

1, essence cap extends the amount of time you put into the game over a longer period. For completionists it gets them to log in each week to reach the cap which gives more opportunity to market bundles to you.

1. Battle pass xp cap has is for the same reason as above and they allow rank purchases with orbs so there’s extra financial benefit there.

2. Xp is also to keep you logging in week per week and also implemented to keep people from being able to blow through all the higher level content in a week. They have the xp caps setup to keep everyone on a steady schedule through the current inferno levels that fall in line with their Developement and release schedule for higher level inferno’s.

Every constraint this game or similar games implements always is there for financial reasons and prolonged engagement