So if you need a framework so you can pretend to have a native version of the application
No, you need a framework so you don't need to reinvent the wheel for every project you work on. With Sencha's frameworks, I can write a pretty slick-looking responsive site in a few hours (or days, for something larger) that would take literally months to roll on my own (and for the record, yes, I can and have rolled my own, back in the dark ages).
why not just focus on having a webpage instead of a shitty application which is just a web page?
Two reasons. First, it increasingly doesn't make sense to force your end users to download and install potentially untrusted code - never mind needing to maintain separate versions for every major platform you target (oh, you want this on iOS and Android and Windows and Linux and OS X, etc?), when you can accomplish the same result in one nice tidy webapp. Second (and you can fairly call this a matter of personal preference), IMO just about everything looks like crap in a browser on a phone, and even that assumes the browser handles it correctly (yeah, like I want to support Chrome and FireFox and *shudder* MSIE and Dolphin and Safari and Opera, etc - Going right back to all the joys of supporting multiple OSs, woo hoo!).
The concept of a "webpage" hasn't limited itself to some statically published version of a document-with-markup in over 20 years; that model lost so thoroughly that pining for it doesn't even count as beating a dead horse anymore, more like trying to clone a mammoth from frozen DNA.
This sounds like lazy people who want to claim they have an app, when all they're doing is pointing to a web page.
It really doesn't matter to me what you want to call it, whether an app or a webpage or a widget or a three-handled family gredunza, if it accomplishes the intended goal... All just a matter of using the right tool in your box for each task - Sure, you can hammer in a screw, but sometimes a plain ol' nail will do the job just as well.