When I've had the opportunity to audition different cables, I initially think I hear significant improvements (maybe it's my desire to want to hear improvements or maybe it's just "differences" I hear). But a week later when I revert back to my old cables (whether speaker or interconnects) I find myself admitting that my old cables really aren't that bad. And to gain the small improvement, I have to spend a chunk of change. So I easily talk myself out of the upgrade.
I also think one of the big problems is the huge selection of cables - there's too many choices! There's the big names and then there's the mom and pop shops. It's not easy here in the midwest to audition many cables. And I'm afraid that the perfect cable for my system will be out there and I'll inadvertently overlook it. So I'm intimidated into doing nothing. Pray for me!
