pdq: Maybe so, but also these are often handy to distinguish them from other "John Smiths." Of course, it doesn't help with Blind Blake. :-) At allmusic.com (pretty good info & getting better) you see the two him with a choice of Blues (ok) and Reggae (!). But the brief article is ok. You see the phrase: "The calypso Blind Blake (use it sort of like 'Country Johnny Mathis')"   Hmmm. I see from the blues Blind Blake article that he recorded far more than I thought.

And if you look at other bios, you often see that an appelation was won in childhood or self chosen to honor another artist. Eg, Sonny Boy Williamson #2 (for Aleck Miller, who was already known as "Rice" Miller.)

Then there's also the total failure of monikers: If you're looking for a Gary Davis record, you might look (and I have found) him under:

Gary Davis
Davis, Gary
Rev. Gary Davis
Rev. Davis, Gary
Davis, Rev. Gary
Blind Gary Davis
Blind Davis, Gary
Davis, Blind Gary