Your parents may be retired and not need to go out. Many in the 65-74 age range do still work, either out of enjoyment or necessity. Some may still need to go places where the risk of transmission is low but not zero (pharmacy, grocery, doctors). Some have multigenerational living situations and take care of older children or grandchildren. In general, somehow... someway... a lot of them sure are dying.
Determining which elderly people fall into a low risk category (like your parents) and those who fall into a higher risk category could be done to facilitate vaccine prioritization... but it would probably be time-consuming.