Obviously the ability to play by ear and the ability to sight read are both important skills to have but it appears to me that once a musician learns proficency at one skill the musician has extreme difficulty developing the second skill.
Thoughts or comments?
Not necessarily, both need to be practiced. As Eddie mentioned all should take music lessons. A good teacher will teach you how to read music along with theory while a great one will also teach improvisation. Both are very important if you are to make it professionally.
With today's technology, mostly BiaB, you can both practice site reading and improvisation anytime you want. The band is always ready!
On a side note back in the mid 60's I was one of the few guitarists that could read music and I could improvise. Because of this I was asked to join a wedding band and as I needed the money I did. That was one of the most important things that I ever did. Site read out of the original fake book and also improvise based on the chord structure. Plus a lot of those songs were not in guitar friendly key signatures, i.e. a lot of Eb, Bb and Ab. I got a great education playing with those old timers in that wedding band.