Not all spiders are buddies who will just keep to their website and kill pests. Many are aggressive roaming hunters that just go around biting shit to see if it is edible. And that includes you just sleep or sitting still.
Also, even the nonvenomous spiders have some seriously bad oral hygiene and carry bacteria that causes deep infectious wounds that take months to heal.
Even with all that, if they were just slow or stupid I might take the time to catch and release, but given that the majority are stupid fast, and/or actively trying to leap at me... they gotta die.
Having said that I don't fuck with them outside, especially the banana spiders, because banana spiders are instantly easy to identify and aren't interested in starting trouble.