Web apps are to native mobile apps as Java apps are to native desktop apps: ploddingly slow with clunky non-standard UIs—a degraded, lackluster experience.
With some notable exceptions I think they can be a pragmatically motivated stopgap step (in regards to either bottlenecks in time or money) on the road to building a full native app. But saying simply that because they cost less time or money to produce as a sole justification for creating them, and ignoring all their shortcomings, is like suggesting everyone buy a circa-1998 Samsung flip phone instead of an iPhone simply because you can get one on eBay for $5. It doesn’t matter, because the flip phone sucks and the iPhone doesn’t—economics aren’t the only factor to consider.
If you need any more proof, remember what happened when the iPhone originally launched and there was no support for building native apps. Apple’s professed solution was for app functionality to be provided by mobile-optimized web apps. There was literally a sustained caterwaul by developers and users alike for the ability to create native apps on the platform, so much so that Apple did a complete 180 on their original stance.