I noticed that too that many people from the US have a problem with letting cats roam, because it might shorten their lives, but it is very acceptable here to let your cats roam if you can arrange access to a backyard or garden even in the city. The general thought is that it has dangers but improves their quality of life so much that it is worth it. My brother's last cats were indoor outdoor and they lived to nearly fifteen, despite the cars and the fact that some asshole in his neighborhood actually shot at them with some sort of air rifle, which my brother only noticed long after when stray pellets showed up in medical scans for unrelated illnesses.