The reason I can't read music (well):
1) When I first was learning to read music, I was playing bass, but because I was in a junior high school band and there was no written bass music, I had to read tuba parts (tuba is written an octave lower than bass).
2) I'm mildly dyslexic.
3) While at Berklee, my principal instrument was guitar... and to be honest with you, the guitar teachers didn't expect you to read well... it's just the nature of the instrument. There's like 4 ways to play middle C... reading music on guitar is like being told to read Dante's Divine Comedy in its original Italian... sure, I've tried... but getting lost is inevitable.
3) Since leaving Berklee, I haven't been in a single situation in which I've had to read music. Not notation, at least. I've been handed chord charts a few times, but that's all about knowing music theory, not reading notation... which brings me to my next point...
4) I know theory. Hell, I even give my best friend (an aspiring guitar player) "Theory Lessons" (payment amounts to beer and booze... not a bad deal). Knowing the difference between a vii-7b5 chord and a diminished chord is, IMO/IME, way more valuable than being able to read a couple of dots on a page... unless you are/aspire to be a studio musician which I am not/don't want to be.
5) I wish I could read well. To be honest, I know that being able to read could open doors for me. Luckily, I have a good full time job that pays my bills, and i can pick and choose the gigs I want (I currently play in only one band, perhaps a second on the horizon, but that's all by choice). I would feel more inclined to earn to read well if music was my primary source of income, but it's not... The Wine and Spirits industry is... so I'm more inclined to learn about "carbonic maceration" than how to read... but that's just me.
6) Rationalization is fun.