Why people don't take precautions of covid?

I have seen many people (here also) who think that if they need to wear mask even after getting vaccinated then there is no need to vaccination. Why don't they understand that all the rumors about vaccines are false and it doesn't have any major side effects? Why can't they understand that taking precautions in such situations is very important and it can't be taken for granted only because of likes and dislikes? Are vaccines really dangerous that they can cause serious problems like heart attack or are these just rumors? I have many doubts like this in such topic like sometimes I even doubt are vaccines truly safe because people say it is like taking a life risk while I haven't seen/heard it happening with someone.
Updates
+1 y
Important doubt I have here is are vaccines really safe or not? I'm not in anyone's side so don't give offending opinions. Thank you. And sorry for my immaturity. If you don't like my question then understand I'm still an immature 13 yr old.
Why people don't take precautions of covid?
Post Opinion