Why is Xbox enforcement so soft?

You are forgetting

Moderate trash talk is fine

But moderate not rated r

You gotta remember you don't know who is on the other end

Everything MUST BE rated PG at all times it doesnt matter what the game rating is

It is upto the parent if they buy the game

Xbox live is not rated

Then why can’t the tos say swearing is not allowed

I understand but if I am taking about someone else I don’t know how it affects the person I am talking to.

As noted above, Xbox is "E for Everyone" and so communication must be in accordance with that. Sure, people do and say a lot worse and get away with it but it doesn't matter...using the f word (even mispelled) is against the TOS and thus open for a suspension if reported.

The best thing to do is report any players griefing you, block them and move on.

As to Enforcement getting softer: At a guess, I'd suggest that Enforcement has had to get a lot tougher due to the gaming community in general being so toxic these days. I don't know how they run Enforcement but it would make sense that they would be keeping an eye on everything and clamping down as and when it is necessary.

It doesn't matter

EVERYTHING must be rated E for everyone regardless if you are talking to said person or not

You don't know who is on the other end