Hmm.
With all due respect for everyone who has contributed so far, if one has difficulty finding a bass player (or difficulty understanding the seeming lack of them) maybe we can take a step backwards and see the big picture.
For one: mainstream music has been and will pretty much influence most of the music-playing population. What happens if you're doing somewhat underground or non-mainstream stuff?
Secondly: with regards to "blues" bass players, some folks do take their music seriously and just because to ever-assuming guitarists it may seem like a string of boxed pentatonic shapes, it's a whole different story for bass players.
Thirdly: if you're aiming really high to play incredibly hard, technical songs... just ask yourself how hard is it going to be to find a reasonably players of any instrument, much less a superbly techincally proficient bass player who will suddenly come into your life and play JUST for your band.
Just to share with you guys... whenever I craft a song, unless I have a specific bass line in mind, I would always be perfectly open to letting my bass player come up with his own basslines. That is to say that I respect his choice of notes and unlike trying to force my bass player to fit my vision, I allow him space to stretch out on his own because I enjoy playing challenging riffs. However that is purely in the context of writing originals.
So, what can be done about it? I suppose it's pretty much up to the seeking parties to retain their hopes of finding an already excellent bass player, or what one could do is start a band with a reasonably able player and grow with him/her. Or you could unfortunately be unable to find a bass player due to passe or unconventional genres.
Just sharing my thoughts lah.