for children vs. for adults

Hay guys how come in Japan it's acceptable for adults to read manga but anime is strictly for children (or teenagers at most)?

It's really the same content, right? What the fuck difference does it make if I watch the Azumanga Daioh anime or read the manga? WTF. ZOMG.

No, seriously.

Can't be that anime is unpopular with adults because they have to dedicate time to watching it on TV though. I'm sure Japanese adults watch all kinds of non-serious bullshit on TV.