I'm kind of stunned by some of the responses. People seem to have no goddamn clue. (Internet, what did I expect?)

Also you can have more rough time with them if they are young, and not injuring you or your guest if they panic for whatever reason(like loud noise), or decided to be an asshole to stranger in their space.

To be fair it depends on the cat. When they get older their nails grow slower and are often more brittle so if they have surfaces to hone their claws they take care of it themselves. But yeah if they get too long you always need to trim them. When my cat was younger I used to trim her's with a nail drill. Saw a parrot owner do it that way because apparently it's less discomforting and my cat seems to agree.