You Travel More
In Your Twenties: Maybe you backpack at some point with friends, but often it's hard to synch budgets and calendars to see the world together.

In Your Thirties: Even though your time is limited, you likely have more disposable income and your friends may be more spread out than they were during college (or even right after you graduated). Accordingly, it's easier to plan trips together or to travel to visit each other.