Let me muddy the water. I think an analysis of some observations is in order.
When I volunteer as a safety officer at GSSF events (which are lost brass matches), I see an abundance of 9mm. For every 30 rounds of 9mm, I may see 4 or 5 40 S&W, 2 45 ACP, and if I'm lucky, a 380 or a 10mm case. Most of the brass appears to be factory loaded (noted by crimped primers and sealant). If it were me, I'd shoot reloaded ammo in lost brass matches and not leave behind once fired brass. Very few steel and aluminum cases are present. To me, that suggests that 40s, 10mm, 357 Sig, and 45 GAP are either reloaded or not as popular as they once were in the GSSF matches.
When I take a walk through my club's pistol pits, not much spent brass can be found. What I am finding is a large quantity of spent steel and aluminum cases, 25 ACP, 32 ACP, 32 S&W Long, and a large quantity of 223 (most likely left behind by the police departments that train at our range), along with a large quantity of spent 22 brass. Rarely do I see many 38 Specials or 357 Magnums. Up until this past spring, you could spend an hour in each bay collecting 9mm, 40 S&W, and 45s, but revolver cases were scarce.
For our mid-range and long-range matches, none of our competitors leave brass behind.
Based on what I don't see, I believe that 38 Special, 357 Magnum, and some 44s have been reloaded since the scamdemic began. Of late, there appears to be an increase in reloading 9mm. I would suspect that few people are reloading the 223 that has been left behind because of the crimped primers.
Also, if you look at the sales ads for brass recyclers, revolver brass is scarce and higher priced, suggesting that while it is not a common cartridge, the brass is in high demand.