Customer pressures. Don't want to pay for iPhones ('too costly'), and then for long very hard to optimize for Android ('why too slow?') (even native... wait if native why slow? Because they buy the worst, cheapest androids ever, then later buy androids that cost similar to iPhones, so it was a big switch cost for nothing at the end)
Eventually, it became nice because it worked to give the app a wider reach. Then I added an e-commerce front, so it made sense. But is it less costly than native? Not.
So, hosting doesn't cost?
Too many app-but-websites should be local, but because are web requires hosting and likely a database (that must be 'web-scale' so it survives bots).
My web app cost far more than my older native one. And is far harder to maintain...