Prepositions can be one of the most bizarre and confusing parts of English.
Sometimes they’re part of a phrasal verb (“She just can’t give up talking about her new horse.”)
Sometimes we’re never sure which one to use (“Is it ‘in’ Wembley or ‘at’ Wembley?”).

Sometimes they’re just there. For no reason. Just hanging out with some other word: (“Don’t point at people! It’s rude!”).

This last point can be tricky for learners, particularly when we sometimes use the preposition and sometimes don’t. Compare, for example, “Wait for me!” and “Can you wait, please?” Why was there a preposition in the first example, but not in the second?

One way of explaining this to our students is by telling them that we use the preposition when we use the object. But a lot of students get put off by even mildly technical terms like “object.”

Another way of explaining this is with the “preposition bridge.”
I made this video to help explain to students that use the preposition bridge to connect to an object. No bridge? No preposition.