If they just didnt give gold when you hit certain levels there would be less incentive to bot in the game. Now blizzard is just begging for a bot or two to be created.
I would only Bot it to level an account or character in Versus A.I. with A.I. Teammates toggled on. level 30 and 40 seems high for ranked modes and I want level 10 on some characters to unlock the "master skins" along with the 1500 gold from level 15 and 2500 gold from level 20.