Shouldn't plugins code be all in plugins?

[rica-carv]

Shouldn't plugins related code be all in plugins folder itself?

I'm asking this because as it is now, tehre are severall plugins that have code, shortcodes & templates scattered around the e_107 core.
For instance:

• News plugin: Has code inside the print.php, there's a submit_news.php file in the root of e107, has a news_class in handlers, etc...
• Comments plugin: Only has a menu in teh plugin, all the related code is also scatered across e107..
• and so on...

Imagine if i unisntall news or comments, or any other plugin, as matter of fact, should all the related code also be uninstaled, without leftovers?