Well, if you DON'T clean the barrel, there are other problems that weren't mentioned.
For one, carbon fouling collects moisture like a sponge. Unless your barrel is stainless steel, it WILL eventually pit, rust, and become worthless. This obviously doesn't apply if the weapon in question is a showpiece stored in a controlled environment with almost 0 humidity, but if it's for a carry piece or something that's used outdoors in competition? A wet day will really throw things off.
If you shoot nothing but copper jacketed rounds, no big deal other than bore diameter will eventually change as the copper collects everywhere.
Lead will do that exact same thing, except much quicker and more extreme. It will collect and collect until it turns into a musket. If you shoot any lead, you NEED to scrub that sucker out after every session. With lead it will happen a lot sooner than anything else, but you get the idea.
Will not cleaning it hurt? It might depending on conditions, what ammo is used, environment, and what the barrel is made of.
Will cleaning it hurt? No. Unequivical no.
YMMV, but there's
one guy saying don't clean, and we have hundreds of years of evidence to the contrary, saying we DO need to clean...
But, hey, it's your barrel