This may be opinionated or whatever, but I think its a fair question to ask.
So everyone at my job is like onboard with HTML 5 and whatever. I think its good to have this functionality possible in a web browser…
HOWEVER
For every different device wouldn’t you need to support different versions of your HTML 5 application? Is that so much better than just programming a native application? Is the only benefit in this type of usage the fact that you can create one application with essentially different CSS/JS files?
I don’t really understand why you wouldn’t need different sizing libraries for, say, a tablet vs. an Android m/h-dpi device vs. an iPhone. They are all different, shouldn’t the browsers render differently on those devices as well?
I know HTML 5 apps have features that allow it to act like a native app, but if you would need to resize your app for every device is it normally worth the tradeoff?
It’s a buzzword. Buzzwords make marketing people happy.
For the rest of this answer I’ll assume you mean “What is so good about HTML 5 when it comes to mobile devices?”.
No.
Even if it was the case, it saves having to port the application to a different programming language and GUI toolkit for each device.