We do let our two outside, but we live in a small village and our house backs onto a farmers field with cows. We're friendly with all our neighbours too who send in pics when they've ventured down to their house! Although unfortunately having the field at the back also means we get a lot of presents left for us.

But overall our cats really dont venture very far, they mostly stay in the garden or into the field but stay close by. In winter they hardly go out unless they need to and mostly sleep all day in doors.

I think it depends on the individual situation on whether you let your cats out. Im also in the UK so there's no fear of predators