> On the other hand, I heard that leather is a by-product of the meat industry - i.e. the cattle would be raised either way.

Sure, but still seem worth it!

Right now the by-product generates additional profit per animal. If we all stop using leather, the by-product becomes a liability and they need to do something else with it that costs them money.

All of this means to retain their initial profit per animal, the cost is transferred to the meat consumer. Which in turn might help drive sustainability through lower meat consumption.