[avar]

Yes we do, e.g. there's a sweet spot when scaling an incline (especially if there's easy handholds, e.g. a grassy incline) where using all fours is much easier and natural than making the same trips on two legs, even though you'd be perfectly capable of doing that too (i.e. I'm not talking about proper wall climbing).

[macintux]

You’re right, but if I can extrapolate from myself to most adults, that’s approximately never.

I think I’ve done that once in the last 10 years, and I spend a fair bit of time in the woods.