Not everybody.....Grandmas on their laptops, non IT people.... some kids. Most of those people would probably never realize they had a quad core in their machine.
Yes everybody! all of those people need quad cores. Why? because quad cores will provide a superior, faster, smoother experience.
You think just because someone is old / young / computer illiterate that they like waiting forever for tasks to complete?
heck, I find that those people need it the MOST because if they are sitting there waiting for something to load they get bored and start doing bad things... like running it again and again because "maybe it didn't get it the first time" or cutting the power because "it is frozen" (it isn't).
Every old person and child and computer illiterate I know can tell when his/her computer is faster slower. And none of them should be trusted with a slow computer because of the damage they do when forced to wait (and then I have to fix said damage).
Example... windows starts installing a windows update automatically... the computer feels slow... so they cut the power in the middle of the patching process, corrupting windows files. Yes, this actually happened. When asked why did they cut the power despite being repeatedly told not to ever do so? well... no reply...
heck, Worse I had was:
Me: It seems you have a virus, I will come by tommorow to fix it... until then, whatever you do, do NOT go to your bank website and log in or it could steal your password and money.
Computer illiterate: ok
Next day I found out that they went online and did their online banking... because "I needed to and its not like did any harm".
You have both too much and too little faith in people... too little faith in their ability to tell the difference in speed or ability to multi task (and by multi task I mean having a minimized game running, 10 excel / word / powerpoint documents open, dozens of web pages, and several other productivity programs running at once; I even saw some run multiple games at once (run one game, minimize it, run another game)... And too much faith in their ability not to break their computer.