Dubbing is usually a thing in countries with large populations. I assume it started when English proficiency was much lower and someone thought it was worth doing it instead of subtitles and then they just kept doing it. These days in Germany the big cinemas offer showings of some movies in the original language, in the past (well, for some movies still today) you had to go to special cinemas to see a movie in the original, so things are slowly changing.

Now, why do these countries dub everything I don’t know

Keeping the language alive and available to other people outside of face-to-face conversations.

One of the frustrating aspect of learning a language has a lower number of speakers (let's say under 20 millions) and dubs everything is that you can't really find content in that language to learn it. I learned Dutch for many years, and it's always kind of frustrating to not being able to find that many content (e.g. Youtube video essays for instance) as Dutch speakers would naturally produce that content in English to have a broader audience.

Which makes sense for them, but then brings the question of how relevant the language is. The Netherlands are experiencing the progressive disappearance from Dutch even more as more and more people are coming to Amsterdam and other Dutch cities, and aren't motivated to learn the language, as English is so widespread everywhere. Young Dutch speakers also tend to use more and more English in their slang.

I kind of have the same situation as I'm learning Catalan, as most of the Catalan Youtubers produce content in Castillano rather than Catalan to reach a broader audience, but then the language becomes less and less relevant. That's one of the reasons Catalans want to keep movies dubbed in Catalan, as it is a way to keep it relevant.

I'm really torn between the two approaches. I get people who say that everyone in Europe should just use English and be done with it, but at the same time, Romance languages just hit differently. It's part of the local culture, and I think it would be a waste to just let all of that disappear. Another example I have is someone I know who's perfectly proficient in English (lived in an English speaking countries for many years), but still wants to raise their children in Dutch. So at the end of the day, is that language still relevant or not?