Do you feel the same about a helmet?
Well if you want to be silly about a subject, let's consider if you fell on your head would knee pads protect you from the consequence of the fall?
Now let's get serious about bike safety for just a moment. Helmets of course, in every situation riding a bike. Proper footwear? Again, of course!
How about clothing of a specific type? Well, it all depends on the situation doesn't it?
What I mean to point out here is that knee pads and any type of outer wear maybe appropriate depending on the biking situation.
I never thought because of my double knee replacement that it may be safe to bike only with knee pads. So in fact I have never worn knee pads while biking. I do own knee pads and have found them helpful when doing tasks that involve kneeling. And I can imagine it is possible that on certain trail type riding situations knee pads could be beneficial to wear. Try this link:
https://www.rideguideblog.co/2014/08/20/crash-without-the-burn-all-mountain-mtb-knee-pad/
I have been thinking like an old man who has had two total knee replacements for about 8 years now. I have no plans for MTB cycling -so probably won't be wearing my knee pads on a bike ride. I mostly bike commuting to work -don't need knee pads in that situation. Now, I'm thinking some people could be wearing a set of knee pads to work -it just depends on the work.
Finally, having experienced a serious bike accident, a helmet saved me from more serious injury:
http://bikejournal.com/blog.asp?rname=bikerjohn&cdate=3/25/2010
bikerjohn 03/24/2010 -after a mishap on a steel decked bridge.
Chopperbill, take my advice and be careful out there.