why do people feel the need to buy expensive cable

The reason people often state that expensive cables will not make budget speakers sound better is because the budget speakers drivers are limited in their excursion . The more money one spends on speakers generally the larger the drivers will be in the statement speakers . (harder to drive to their full potential ). Thus cables that can send the proper amount of current is more important for those speakers . Hence being able to hear large differences in cables in those systems.

Bravo! , we'll said Mike, I've done experiment's with taralabs cable's since the introduction of earlier ground station's of the mid 1990s, you can pm me and I share a few with you, also, at one time, I had the Taralabs, the one with two mono blocks grounding station and one stereo grounding station, all on the same interconnect! , talking about low noise floor that was not supposed to be heard on this model interconnect.

Ohm's Law suggests that if you desire more current to the speakers all you actually need do is reduce the length of the speaker cables. While this may or may not solve you particular concern regarding woofer excursion, I tend toward suspecting that increasing the current by itself will solve the other issues involved not related to woofer excursion. Such as grain in the treble, soundstage depth, resolution, tonality, frequency response, dynamics and inner dynamics, warmth and sweetness, to name a few.

Addendum to my last post: Ordinarily when one requires more power, I.e., current, to the speakers one simply turns up the volume knob, no?

Expensive cables don't cange your amp"s sound. Your amp is what it is. Cables ADD there own sound to give you the illusion of "unlocking" something magical that cheaper cables were unable to.