@Ernest Bywater
These are just two of the situations where I know the fonts are proprietary and need to be licensed for use. I also know Crumbly had a big issue with getting licenses for some of the fonts he wanted to use.
For the most part, I know what's required going in. but ... there are also fonts posted to ALL the font sharing sites, for which there is no known author, or the author is unreachable. Those cases are frustrating, but in those cases, the assumption is that, since no one complains about the widespread distribution, and there is no one to contact, it 'acceptable practice' to use it as long as you put a disclaimer in, specifying that you've searched for the designer, and request they contact you directly. That demonstrates a 'concerted attempt' to contact the designer.
I ran into this was font released by a now-defunct game designer. For such a public source, you'd think the designer would be known, or that the gaming company would have kept records, but alas, neither is the case.
However, that was the ONE case I couldn't resolve.
As for private propriatory fonts, I regularly visit dafont and several other font sites (font designers often cross-post to multiple sites), checking out the latest designs. It's often easier finding particular fonts from freelance designers than wasting time checking out big-name design studios (who often change hundreds for 30 or 40 fonts, when all you need is ONE).
I frequently use cover/title fonts which match the feel of the book (like cowboy fonts for westerns, gun (shot up) fonts for mysteries or sci-fi fonts for sci-fi stories). By giving readers a way of visualizing the story, it helps immerse them. Plus, boring fonts without any real soul are worse than not even including the title on the cover (in my honest opinion, after having done that for quite a while).
But, in the end, using fancy fonts for books is a personal pleasure, as it WON'T add a single sale or increase downloads or increase scores. But as I typically change more for my books ($4.99 - $5.99) than most independent authors do ($.99 to $2.99), I feel the extra effort makes the extra cost worth it.