*shrug* It was there, in the store. I've been waiting for a copy to come in for
two years, and ordering it there is a total PITA, so I've just never bothered with that -- and every time it comes in, it's gone half an hour later!
Aside from that, there's also other practical reasons. At the moment, I'm reading a *lot* of treble clef. The only non-method book I have in bass clef that I use is my Mingus More-Than-A-Playalong -- my bass clef reading comes in the form of this and my music for jazz/concert band (including reading those confounded tuba parts.) Every day though, I'm sight-singing in vocals class (getting decent at it! Still don't have a nice voice though :O ) and I'm reading the heads for my audition songs and other tunes from treble-clef leadsheets out of Real Books.
Also, were I to ever lend it to a friend, most people do not play Charlie Parker on bass-clef instruments. And if they do...well, this is a nice workout

.
EDIT: But, mostly just 'cause it was there. So what're you playing out of it, Pete?