And it's about more than just the brass. Loaded FMJ 9mm ammo works just fine for most practice and is generally cheap. .357, .41, .44 Magnum loaded ammo is almost never cheap. So while you can practice "enough" with a 9mm... odds are you won't ever be a great magnum revolver shooter unless you reload. (OK, if you are willing to spend literally hundreds of bucks on ammo... I can't imagine it.)
Plus the revolver rewards the reloader in even more ways. My very favorite "knocking around" .357 revolver round is a hard cast double ended wadcutter. (DEWC) It can be loaded faster than the typical swaged target hollow base WC's. I usually still keep it well under 1000 fps but a hard flat wadcutter hitting a small to medium animal at 850 fps or so will usually do the job. If I didn't reload them... where would I get them?
I like to load absolute max WW296 loads behind a Sierra 180 JHC bullet for my 9.5" Super Redhawk. I load them so hot they flatten out the primers most of the way.. I wouldn't shoot that load in another gun... but that load in that barrel with a short pistol scope on top... you can totally smoke most vermin! Where would I buy that load?
I could go on and on. Revolvers can be loaded super light or, in some cases, super hot. They can handle light for caliber bullets or heaver for caliber bullets. They can handle any standard bullet style as well as full lead SWC/WC/HP's whatever. Nothing to get stuck on a feed ramp and cause a jam.
I do reload for my autos because I'm not made of money. But in my case, reloading for those autos is nearly entirely about saving money. Factory ammo works just fine... if you have the money. In my revolvers, I like to save big money... and get lots of kinds of ammo that I couldn't find to shoot otherwise.
First non-.22 handgun... Ruger Security Six. Stainless. Six inch barrel. 21st birthday, 1982. Bought the gun, one box of factory target WC's, one box of Federal 125 grain JHP's and Lee reloading dies. The little cheap kit that you sit in the floor and hit the cases with a hammer! But it worked, I learned how to shoot that revolver, I never bought any more factory ammo for it. Still have that gun. Right next to the bed. Lots more "up to date" handguns in the house but I have total faith in that Ruger and in my ability to use it under stress.
Gregg