It's also very important to know how to properly "roll" your cables, using the over/under technique that stagehands use:
I do use this technique, and it does a good job of keeping a cable from getting tangled with itself.
I also have a pre-wired rack
In spite of that, cables in a suitcase that gets jostled in transit tend to tangle with EACH OTHER no matter how they are wrapped. The bags keep the inter-tangling from happening.
I once heard a band mate describe it like this:
"trying to take one cable out of a tangled mess is like trying to take a small sip out of a spittoon... it all comes out in one big glob"