You can’t keep cats inside all day for their entire lives. They have to go outside, usually just to roll around in the sun, have some fun, or take a dump.
My parents have had cats ever since I can remember, the cats spend most of their time outside and never has one been killed by a car accident. One of our cats is very old but hes still doing just fine probably because he spends most of his time outside (watching over our territory for intruder cats from the outside world :3)
It would be impossible for us to keep the cats inside, they will trash the whole house if they have to.
We also have cats from other people coming over sometimes, to eat food we put there or to play with our cats.
Sorry for your loss Shadi, I know how it feels to lose one of them cuties.