First, some people in their 20s and 30s are students, they were forced to take morning exercise when they were in high school, so when they graduate from high school, no one force them to exercise, most students become lazy and enjoy sleeping for the long time. Only small portion of them can stick on the habit.
Second, other people at such age are having works, they are fighting for their career, the pressure in so great that they have to sit on the office all day. Out of such reason, they have to work in the office for long time to compete with others. The fierce competition makes them can’t take breath, people have to work as more as possible to ensure the boss is satisfied.
People in the 20s and 30s are in the good time of life, besides sleeping and work, they should have some time to take exercise, the healthy body ensures better future.