You’re going to need a very good and viable replacement in that case. And due to niche cases like Crenellations Castles, it needs treb style range. So there’s no point.
Turks don’t technically need trebs.
Nerfing Turks by removing trebs would be a bit dumb because Turks are already weak in situations where they need trebs, but it shows that it’s possible.
I don’t think you always need an answer for niche cases. It’s OK to have civs with some matchups that are very hard for them to deal with. A civ lacking Trebuchets would likely have a different Siege alternative.
Who knows, maybe it’s a Siege Archer, like some sort of a ranged Tarkan!
trebuchet can come out of castle asap starting in imp. you can’t do that if you haven’t research chemistry and it is expensive to research it in castle age, almost never.