Why make a suggestion rather than asserting it?

Question

A few days ago, I posted a question in a different community where I observed an interesting piece of sentence. Here's the link. In the first comment:

"there's a lot of restrictions on using costly instruments in private colleges whereas we get a lot of liberty to get hands-on lab experience in public ones": I'm not sure this is an inherent difference between private and public institutions. Couldn't it be that the institutions in your experience simply had different policies or cultures, that just happened to coincide with their public/private status?

The person writing seems to be older and knows a lot more than me regarding graduate school. Instead of writing directly and asserting the point, he puts it as a suggestion. Likewise, while interacting with many people, I have observed similar speaking styles in a number of occasions. My question is why do they write it like that? Is it some kind of writing style? Or is this simply a manner thing?

Answer 1

You only assert when you're sure of things. This person might think it's very likely that it's merely a coincidence that these cultures and policies are correlated with public/private schools, but unless he knows the schools in question, it's bad form to insist that it is coincidental.

Suggestions also tend to make people less defensive, they lead to the correct answer instead of throwing the answer at you, making you want to deflect it.

This feels more like a psychology topic than an English topic. I'm not fluent in other languages, but I'd imagine in at least several others this same type of suggestion is used.