Possibly the practice of not using the cap or rim nut goes back to the days of tubular tires. With tubulars, I never want anything that could trap the valve in the rim if I were to roll a tire. It could be the difference between riding a rim (and probably destroying it) and a locked wheel causing a more serious crash.
It's a habit that sticks with you, so today, even on my PV mtn bike tires, where it doesn't matter either way, I still don't use the cap or ring. As far as I'm concerned the only purpose of the valve cap on PV tubes is to protect the tube from puncture while it's still a rolled up spare.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.