Pickers are very specialized:
They don't have to be. I am pretty fluent in about a dozen collectible categories and sharp at 6 or 7. I used to appraise a number of them.
Its true that just because you know electric guitars, or guitars in general it doesn't help you much with violins (man do I -ever- know that!! They were always trying to dump fiddle appraisals in my lap).
But still, the more you learn, the more options you have.
yours Scott