[fknop]

It's a "random" guess. But in my experience, for a website, if it doesn't look good at first sight, a user might just leave instantly. As someone pointed out in the comments, just looking at sites like:

https://riverbankcomputing.com/software/pyqt/intro https://electronjs.org/

Your eye will probably be more attracted by the good design of the electron website.

I'm not saying an app should be only good looking, but it's clearly a major part.

[Zancarius]

I'm sure that's part of it, but the primary usability studies I'm aware of have all focused on speed/response. Whether this translates to "native" apps or not, I'm not sure, but certainly for the web, response times are king [1]. Curiously, this metric has been a stable predictor of retention for decades (see the sources in the link as it'd be redundant for me to post them here).

[1] http://ixd.prattsi.org/2015/04/response-time-is-speed-the-ul...