The fear of making a bad first impression and potentially screwing up a a potential friendship.
The fear of rejection. The fear of coming off as awkward, embarrassing.
And so, end up not opening your mouth "There's always another time. Can always reach out another time" - and then never do, too afraid to potentially close a door to a potential friendly relationship with someone, relationship that never started.

I'm lead to believe many people those days face this issue. Internet helping in some ways, while sabotaging others. I'm down to chat about it if you'd like, or potentially recommend a few books that I've been reading myself as well as recommend a channel or two on Youtube that provides some valuable information & advice - even though it's quite easy to just binge-watch a lot and then not have anything stick, and end up just wasting your time. Important to intake some and not just toss it aside like a never unpacked baggage or mail, but make revisions, write some of it down, and try to put it into practice.

Thanks for your reply.
I would love to chat with you. Thanks. Is it okay if I add you on discord?