For the really large cannons useing stone shot saves on haveing to cast multiple pounds of lead.
Think of Mons Meg with it's 20" bore and 175 kilograms (386 lb) cannon balls.
It has stone balls because if made from lead a 20" inch sphere would weight in at 6232.69 kg or 13740.7 lb !
That's a lot of lead, and there best not be any hills on the path from the foundry.
Each shot is also worth a fortune and almost immobile from the weight alone, how do you load something that heavy?

A 175 kilogram ball can be lifted by a few strong men, a 6232kg one needs a massive crane, that limits you to ships, forts and siege emplacements.

Even later guns tend stick to shot of below 910kg tops for Palliser shot. (Yes that's the Armstrong 100-ton gun shell weight)