New Android User - one gripe

So, i just moved from Windows phone (was on WP7.8) to Android. Was tired of waiting for a new phone that Microsoft and Nokia just weren't announcing, so I made the plunge, grabbed a new Galaxy S5.

So far, I'm loving the phone (don't get the hate, it's a high quality phone with a great camera. love the pictures I've been taking). But...I have one complaint with the OS so far. If someone sends me a message, it naturally goes to the notification bar. Cool, i like that. But, if I go into the app (say, Facebook messenger) before I go into the notification, the notification stays on the bar! Why??? This seems an easy thing to get right, i hope Google fixes it. If I've seen the notification, it makes sense for it to disappear.

That is all.