Premiums climb quickly with age, especially post-7 years, the actuaries having done the math I presume on chronic conditions.
It's similar for dogs, but even in the early 80s, the average age for domestic cats to die was 7-8 years. Thirty years later it's 15 years. A combination of neutering being routine, more indoor animals, and expectation of better veterinary care. I'm pretty sure when my grandparent's cat got sick, they didn't rush it off to the vet like ours. Certainly, they wouldn't have spent a fortune on chronic conditions.