I've made sure to configure the browser to allow zooming on any website. Don't understand why websites try to block this.

On mobile, zoom can be annoying in certain webapps. It's easy to accidentally zoom in while playing a game, for example.

Is web the wrong platform for these types of experiences? Perhaps, but it's also the only way to avoid the walled garden.

Because they want their website to look and feel exactly like an app. Because users expect apps, presumably. Because modern life is rubbish.