Different times and don't think Zoo Tycoon wasn't considered as a big title. Not even close to the Sims1/TheSims2 which were released at the same time.Yup, because Zoo tycoon was so big in its day and PZ is not and there is probably a reason for it.
They did really well for a niche category
But even among the EA games, TheSims stands out in their support. Most EA games are released as finished (features) and maybe 1 or 2 DLC in the first 6 months and they move on.
It's really a shame, some of the popular games only get a little extra content after release. Assassin's Creed, GTA5/Red dead Redempion 2 (singleplayer), Hitman are among my favorite franchises but you know you're not getting much extra content for the game (update or DLC). Basically you buy the game as it is.