The idea is that most people will never go beyond first or (very rarely) second page. And as said in another comment, if you did not find what you were looking for in the top 20 results, changes are you will not find it in following results.
We do have plans for a feature which would allow community-based alterations of our core ranking algorithm which might help here. You can read about it here: https://brave.com/goggles/
Disclaimer: I work on Brave Search.
I’m willing to concede maybe I’m an outlier in behavior but I definitely want more than 20 results perhaps 33% of my searches.
I wonder if cliqz did any studies on this before deciding on 20 fixed results.
It also conveniently allows them to avoid the issue of paging search results.