Most cats and dogs are kept as pets up to ages where they would be pretty lousy food.
We have superior synthetic glues today, so the glue factory is not an option any more.
Besides shouldn’t we have funeral options for people to permit giving their carcasses to dogs and/or cats, assuming this is copacetic with the family?
You raise an important point.
If, as I've stated I'd be reluctantly ok with commercial use of euthanized dogs or cats, commercial production, which your comment on "tenderness" leads to, would be an entirely different situation.