It's pretty important for two reasons. It's more aesthetically pleasing, organized, and will have better air flow since the wires won't be in way of the intake fans.

Generation wrote It's pretty important for two reasons. It's more aesthetically pleasing, organized, and will have better air flow since the wires won't be in way of the intake fans.

Yeah thanks, but there not in the way of my fans though, its just my power supply cables and there just in the bottom of my case

if you cant see into your case having them tucked to one side or at the bottom doesn't matter.
having good cable management will improve airflow and give better cooling results

as long as the cables don't go in front of anything that needs cooled or in the way of the fans air flow its not that much of a problem but Most cases allow you to tuck the cables behind where the Motherboard attaches to the case