Cool/fashion is only important in what it does to the price, and getting the name in front of people so they are aware and can at least try them out.
Other than that, I suspect most of us aren't affected by 'coolness'. (Even as I write that, I'm doubting it! )
It must be a lot to do with past experiences and influences: when I think of a bass, I always picture a Thumb - always have. I think it's because I used to walk past a bass shop on Denmark St and see one in the window many years ago, and it was the picture I had in my mind ever since whenever someone mentioned bass. The fact that they sound so funky just cemented that.
Doesn't stop me trying other (cooler?) basses out though.