What factors can increase my cat’s risk of getting fleas and ticks?

I generally find with kittens and old cats, meaning those that are not as thrifty as they once were, they don't clean themselves as much, or those cats that go outside are at much greater risk of getting fleas and/or ticks. But I often see kittens and really older cats being much more of a risk because they don't have the tendency to clean themselves and remove these external parasites called fleas and ticks. Age can be a factor, and the more time they spend outside is a risk as well.