Moved to the suburbs in my 30s. Got a new bike to hit the nearby bike trails. First bike ride turns into agonizing ordeal as it literally feels like someone ripped open my knees and poured broken glass in them. Diagnosed with arthritis in my knees.
There are plenty of reasons people don't use bikes, and health reasons are one of the main ones.
Based on your comment, it's pretty obvious to see that you don't have arthritis in your knees, otherwise you'd know that biking requires you to exert force to push down on the pedals, thus exerting force on your knee joint. Whereas walking is just lifting and lowering your leg, with no force exerted on the knee joint.
In other words, you don't have arthritis and have no clue what you're talking about.
Oh, I wasn't saying specifically in your case, I was just saying generally. We got loads of out of shape people who would balk at being told to ride a bike, even though it would be easier than walking for them. Sorry, I wasn't particularly clear with that comment.