Is it "scary or dangerous" for someone to know that you like them?

I myself have no clue why someone would not be willing to let the person they like, to know that they like them. It makes things much easier and quicker than to leave lingering feelings and thoughts of “unrequitted” love and whatnot to the point of enfatuation and the extreme of obssesive thoughts of the said person. So why doesnt someone just go up, ask, and either get rejected or accepted? What’s the worst that could happen? Them saying “No.” Hmpth. As for if this is a rhetorical question, not so much as for reasoning of past actions of my own and select others.