why do people feel the need to buy expensive cable

"True That . So the designer of amps and speakers should have the knowledge of what is needed to make there designs perform optimally . Why not tell the consumer ? "

They can't be too specific because its impossible listen to everything in all possible combinations. Also factor in personal taste.

Most manufacturers do give some general info on how to get the best from the speakers, in the owners manual and/or online. Another option is to call them directly. If you tell them about your system and taste, you usually get much more info out of them.

"They can't be too specific because its impossible listen to everything in all possible combinations. Also factor in personal taste."
The personal taste was in choosing their product . Sell the product with the knowledge of how to get the very best performance from there product

Who likes going around the merry go round over and over , Start to feel dizzy after a while . How many of you like to feel you may not be using the right (best) cable ? No interest in buying fifteen different cables to simply find the one that has the proper design to fit a particular piece of gear .

"Most manufacturers do give some general info on how to get the best from the speakers, in the owners manual and/or online. Another option is to call them directly. If you tell them about your system and taste, you usually get much more info out of them"
I find the power requirement specs a joke . Magnepan for example states something like 100 - 200 watts for their speakers . Not much info there . same goes for all speaker specs i have read for speakers bought in the past .
Lets use the sports car analogy once again . You buy a supercar but they leave a crucial aspect for performance up to you to decide . Unless you are a car designer you are not going to want to make that choice on your own .

No manufacturer will knowingly publish something that might limit sales. That's why most speaker makers understate what power is needed for best performance. It would scare off potential customers in many cases if they told them how much power was needed for optimal performance.