Why don’t you participate in the portal’s tournaments?

I don't see the point because I'm not very good. I don't consider myself a strong enough player to start participating in tournaments.

In my opinion, that's not the best excuse. When I first came to this forum, I was a complete noob. Now I've grown to be just a noob, and that's all thanks to tournaments, so I don't think there's any reason to be afraid of them!
P.S. Regarding the topic: there are no such reasons – I play in almost all tournaments, except for those that take up a lot of time (for example, a paired tournament for maps).