Fair enough - two archers in our club use slip on armguards, not sure what make (possibly Bohning) but quite a few just wear a bit of cheap tubular bandage / tubigrip under their usual guard.
For
longbow I do this - I don't hit my arm with
recurve & wear a very narrow Bohning guard but have caught myself a couple of times with
longbow (just learning the basics of technique) so I go for the extra protection.
Two possible side effects of the slip on guards are in the summer - can be sweaty underneath on really hot days plus you will have one white forearm & one tanned one on a long days shooting
Karl