I would say the opposite: Why are their lives so short?

The peeps die in their early 60s, generally. A 65-year-old is rare, and a 70-year-old almost unheard of. That's 10-20 years earlier than in most modern first world countries. The fact that they slow down so much at 55 is also unrealistic. Most people nowadays are fit and active until they are 65-70, often a lot later.

It's obvious Arthur is still a young man!