Skills you don't need, atrophy. Skills you need, don't. It's very simple, and the "you won't have the skills you used to need but don't need any more!" line of reasoning is tired and invalid.

That's not how it works, unfortunately. Skills you use stay fresh, skills you don't practice get rusty and fade away. You might need things you aren't using anymore.

If you never walk, your legs get weak, you gain weight, your aerobic system loses capacity, and you lose the ability to walk. You don't need it, you say, because you have your car and your mobility scooter and you'll always have these things. Your crutches don't make you weaker, you can still do everything the walkers can do, you say.

Good luck with the nature hike!