Sure they can be stimulated - but to watch a cat outdoors while it's silently stalking its "prey" (be that a mouse or a fly) for hours on end, watching that alert little face, tense body, wiggle of the tail and snicker of whiskers - you will
never see that (like that) with a cat indoors.
Yeah sure my cat loooooves playing chase and stalk the fluffy wiggly thing on a stick - but it's not the same.
And for them to have a good old stretch in a sandy sunny patch - how can you compare that to staring at a patch of sun from a windowsill indoors
Or watching life pass by outside with a forlorn sad look sitting on the inside. Believe me, it breaks my heart.
My current cat is 100% indoors and I know that under the circumstances it's best. But if I could allow him to go out and do the things cats do, I would.
Yes, of course there's the absolute endless catfights, disease, abscesses, feral issues & death (and much much more) to deal if allowing a cat to roam outdoors. But to me that's a small price to pay to live a happy life.
My boy that died, was a cat that could not stand being indoors. Absolutely nothing I tried worked. In the end he was sent to my mom's where he could roam outside - and the difference in his temperament was like night and day / chalk and cheese. He changed into a relaxed totally chilled cat - as opposed to a highly charged, immensely frustrated, angry and sad cat.
Yes he died under the wheels of a car - but I'm happy he died a happy cat. He was in another country on another continent when my mom phoned me with the news - and I was gutted & heartbroken and sobbed for days.
But above all I'm happy that he couldn't have been happier in the last years of his short life.