There are elderly who can lift much more, but also those who have trouble walking. The small ones can easily be kept in your auto without taking up much room. Let folks take their choice.
I am 86 and had a staph infection in my lumbar spine in 2008, and some days I have trouble walking without a walker. In addition I am now having hip problems. While I can handle the 18 pounds I find it simpler to use a lighter one. I don’t think it takes 18 pounds to lift the hood of my Toyota Sienna, but never had a reason to find out.

I was hunting in the mountains and carrying deer out on a packboard at your age, but it only takes a heartbeat for big changes to occur.

I change my car batteries about every 4 years. I don’t consider it very wise to try to get the last 6 months out of a battery since today you have no warning like the old days. I do the same in the case of tires, especially since I can no longer change a tire.
Regards, Jerry