Honest question: do they? What evidence supports the assertion that they do try? I haven't seen any story suggesting Mozilla is trying to get away from that model of funding Firefox.
> "(how to get people to pay for a browser?)"
The Thunderbird email client (formerly maintained by Mozilla) switched to being independent from Mozilla and asking for donations; so far they are successful. Donations are now sustaining a team of 15, thanks to yearly 2.3 M$ donations [1], and they keep hiring.
"A team of 15 isn't remotely enough to sustain Firefox", you may say, and you'd be right. But then, if Thunderbird is able to find enough donation money for 15, what would Firefox (who is way more popular than Thunderbird) be able to score if it found the courage to make its case to its users, and ask for money? Could it afford a staff of 150? More?
[1] https://groups.google.com/g/tb-planning/c/-jbmYvYdX1g , https://www.reddit.com/r/opensource/comments/m9td33/thunderb...
Sure, DDG might be robbing Peter to pay Paul, but so is Mozilla. They sell out every FF user who does not change default settings. This must be a significant number of users, because the online ad services company pays millions to Mozilla for that "service". That means heaps of queries coming from FF are "feeding the ecosystem".