Some people don't care about what their bodies look like while others want their bodies to look good and fit. Some people have a certain lifestyle they like to live like being on only heath foods because they don't want to eat junk food so often because junk food can cause weight gain. Some people could be genetically predisposed to being physically active like if someone they grew up with worked out a lot they could want to do it when they grow up and won't want to stop. while if others don't really have people who worked out alot it won't really matter to them.
Hope this helped i have a family of people who work out and my friends parents hate it