Why, good you asked: a native app called NewPipe [1] which eats Youtube URL's and plays videos (and allows the download of such), no more - and that includes no ads - and no less. It only sends such data as needed to get the video. Lately it has started to support Soundcloud as well, I have not tried this yet.
I've started using the YouTube website on iOS because it uses the native video player and is ad-free then (some people put an ad-break every few minutes on documentaries for example which is super annoying)
+1 dropped facebook native app for their web version. Never looked back.
I think the answer is some apps are better on web, others on native.
Videos / Music / Games / Email / Messaging are better native. For actual reading of content (HN / Reddit / Twitter / Facebook ...etc) I find better on the web.
[1] https://newpipe.schabi.org/