Why would I want to be welcoming or positive? While I'm not exactly aggressive person, I'm more like neutral person and I would never want to fake welcomeness o

Why would I want to be welcoming or positive? While I'm not exactly aggressive person, I'm more like neutral person and I would never want to fake welcomeness or something like that. If someone will approach me with question from documentation, I'll never hesitate to answer RTFM and move on. May be that's US thing that everyone must smile and be kind. I was not taught like that, I don't expect that from others and I'll not fake good mood being in a bad mood myself.