When you're a kid, nobody tells you how hard it is to schedule things when you're an adult. It doesn't occur to you when you're a child. You just hang out with your friends when you feel like biking over to their house and it isn't dinnertime. When you grow up, people have jobs, schedules, and heaven forbid children that keep them from doing the activities they enjoy doing, like Dungeons and Dragons.
And the tough thing about DnD is that you kind of need everybody present in order to move forward. You can't keep adventuring and leave the poor druid in the forest to rot. But for those who are dedicated enough, they find a way to make it work. You may have to book it out 2 months in advance, but by golly, you're going to roll that die. And in the meantime, you can look at these memes to keep your head in the game.