why do people have to complain about everything?

I mean for real (this is probably the ONLY serious question i will EVER ask)
i work at a gas station. and they bitch about gas prices, making them prepay, things that dont even have to do with the store, about how cold/hot they are...blah blah
i had one guy say (when i asked him how he was) im above the ground and breathing
WHY cant more people think like that?
WHY do they feel I want to hear their complaining, is it just they are sooo bored they need to whine?
i am asking why they do it. what makes them complain. I am not whining i am wondering
i love how u all think im complaining. didnt know asking questions was a complaint. if i said "i hate how everyone complains" thats a complaint
btw whoever said their bo told them to stop being nice to rude ppl. ur right if people get rude we tell them we wont serve them.
i am not hatin my job i love it. and its not just at my job i hear ppl complain its at walmart whatever. they yell at the cashiers and i just tell them to go somewhere else theres worse problems and i dont even work there. i love my job