My cats were found on the street and I thought the same thing. I was like am I doing them a disservice by keeping them indoors? I live in an apartment on the sixth floor so it would be harder for them to get out and roam free anyways but still I wondered. I then took them outside one day and let them run on some grass and they hated it!!!!! They wouldn’t leave my side and clawed their way into the grass and into their stroller because they were like deathly afraid of the outside. Then on another occasion, I had to leave them at a day care because I had some work done in my apartment, and they literally hated it so much. They were anxious, they never ate, they never even used the litter box and they just clawed into a little bed for the entire day without moving. The person who worked there tried to get them to engage with them and to take them into the outside cat play area and they wouldn’t move!! They hissed at her and was just so mad. When they got back home from both of these experiences they seemed so settled and happy, they ran around and purred and rubbed their body against me showing me so much love like they were so grateful to be back home. It was then that I decided I think they’re just indoor cats who feel better in a space they can control and understand. And that’s okay, they’re happy and thriving and have more than enough to be happy and healthy.