All the people I know of who had outdoor cats, most of them, the vast majority, like 90% met bad ends.
Getting poisoned somehow, hit by cars, seriously or fatally injured by local animals, accidentally falling off of high surfaces and killing or permanently injuring themselves, and the most common but arguably the worst because it doesn't provide closure: leaving and never returning one day.

Local wildlife decimation aside, I can't get myself to let them out both because I care about them too much but also because I can't handle one of my babies just up and vanishing one day.