Some cats need a little help. Without trimming or normal wear, they may grow around into the foot pad. One of my cats will grow little callouses that mirror her claws and those need to be trimmed. If nails click when they walk, they're too long.
Stan, who passed a little over a year ago, always knew exactly where his claws were. If he wanted something, he would come by, sit and look at me. If I ignored him, he would come up and pat my leg (claws sheathed). If I still ignored him, the claws would come out and he would make a more pointed argument .