Serving an unusable website to end users when browsing on mobile in 2019 is inexcusable. When you are doing it on purpose for your own goals is even worse.
The followings are just 2 example, but this practise is widespread everywhere:
The mobile site is awful, will companies ever stop showing in your face their app? I said that I don't want it 5 times already. It is pointless that you block every single page load with a full-screen pop up to download your app. That's not gonna happen, they only thing that will (and did) happen is that I'll close your website for good and look for reviews somewhere else.
Medium is the worst offender. It's useless on mobile. The whole screen is filled with ads for the app and its premium membership plan.
Is it so hard to understand that I just want to read an article and as soon as I see crap like that the first and only thing I do is clicking that close button and never coming back to your website again.
Apps have their purpose
Apps are great - I'm a mobile developer dammit - I love apps and for most of their uses are necessary. AMP is a disgrace. That said you don't always need a mobile app and in some cases, it just doesn't make any sense having an app when a well designed mobile site will do just fine. I love Apple's policy that an app can't be simply a repackaged website. It needs to have something to make it different and stand out, a reason why it needs access to your phone. Something that it can't do in its website form. That something needs to be useful to the end user. It can't simply be because we can track you better and thanks to that serve better ads.