To be honest Shell, I don't know.... I do quite often loose patience with a lot of the people on there
I suspect that it's a guilt thing - the idea that you're a bad pet owner if you don't do everything you can for your pet, etc... also many will implicitly trust a vet and if he/she says give this or that to ease suffering, prolong life then they will blindly follow instructions.
I do know that with my five younger cats (who are also insured which also makes a huge difference) I'd do loads more for them than I would for Molly. But then she's nearly 21 and I'm sure would not appreciate being prodded and poked at this late stage of her life.
But to answer your question - back in those days 13 or so was considered to be a good age and cats older than that were the exception rather than the norm, whereas now-a-days more and more cats are living closer to 17 or 18 and quite a few past their 20's.... Pets, same as humans, are living longer because of advances in medicine