Exactly. In my case, my Cat had either a) A Genetic Bone Disease or b) Bone Cancer.

Even if he was Human, that doesn't give you many treatment options. Being a Cat, it isn't even an option.

If he were an 80+ yr/old relative, you could just say "Hey, the chemo isn't worth the suffering, but you've had a good run and we'll make the rest of your time is comfortable". But as an almost 12 yr/old Cat, it was "We have to put him to sleep now, he won't eat and isn't doing well" on the spot, no real time to think or get second opinions or treatment options.