It's a combination of (a) Switzerland having a high proportion of renters, and apartments being much more common than town houses or detached housing (b) Outdoor cats still being the norm in Switzerland.
however i keep mine strictly indoors for peace of mind. to satiate that desire to climb and to combat ennui, i built simple cat shelves/stairs onto the wall of my spartment using hand-sawn boards and metal brackets screwed into the studs. there are 2 paths up and down and around the corner that gives them a way to relieve the zoomies when they strike. my older cat uses them to sun near the window, while the kitten both runs and sleeps on them (and other untold mischief).
In the Rest of the World you do have some cats kept indoors the whole time but it is not the normal thing to do. Only in America are they de-clawed, kept inside an apartment for their whole life and not given special 'cat' rights to do things like climbing really 'dangerous' cat ladders.
Cats very much have their own patch to patrol. Their home is there for them come feeding time. Despite being portrayed as antisocial they do interact with other cats in occupying this larger territory.
In a society where people let their cats patrol their territory it seems cruel keeping them indoors. In a street with lots of cats you would let yours out too. But if all the cats are locked away and not able to roam then you would lock your cat away too.
Interesting how Switzerland also has much more cat friendly traffic than what you get in America. Maybe this is why America has become this place where people lock up cats and daren't let them roam freely.
unless you have supportive research in human-feline relations, cat population epidemiology and comparative global felis catus sociology buttressing those anti-american presumptions, my cats will continue enjoying their happy indoor lives.
He's an adult (cat) and can make his own decisions.
I won't let my (small) fear of his death imeped his (great) desire to go outside.
Update: he lived a long-for-a-cat happy life and passed peacefully several years ago.
however your experience doesn't generalize, particularly your assessment of the risks and benefits.
i watched a neighbor's cat get hit by a car and then die in my hands. the mortality rate for cats in my neighborhood is probably north of 20% per year (huge). it would be irresponsible to expose my cats to such risk when they're quite content already. mortality would have to be less than 1% (small) for me to reconsider.