Nobody seems to care that WoW expansions get rolled into the base install later on.

The trick is to have the merge happen a lot later. Like 1+ years, not a few months. That’s long enough that anyone who’s a decent fan and actively playing is going to typically shell out the money. It also makes it easy for new and returning fans to jump in. I’m absolutely certain that there are lots of potential Sims 4 players that see the $500+ worth of DLC and just… never start playing because it’s completely overwhelming. Especially when you see the titles and realize stuff that seems basic isn’t included in the base game: seasons, pets, etc