@DerSchlingel It's like a two-level shortcut. Some apps need to be accessible with a single click, without searching through all tabs. When I start my computer, I want to check my email. I should be able to just click on the Gmail web app, instead of opening Opera, reloading all my tabs, and then clicking on Gmail.
Firefox has built full PWA support, which I believe came from extensive user analysis. There's clearly a demand for PWAs, as many users are requesting this feature. This isn't just a coincidence