Because most new cars use direct ignition as txe said his car does. With direct ignition, each spark plug has it's own dedicated ignition coil bolted to the head directly over the plug. Distributor caps, rotors and wires are meant to direct the high voltage pulse from one ignition coil to one of several sparkplugs at the proper time... If you have a coil for each plug, there's no need for a distributor. If the coils are bolted to the cylinder head, you only need a wire long enough to reach the plug - about 2-3 inches generally. The "wire" is part of the ignition coil housing.
Putting aside the fact that it doesn't apply to this situation, unless the OE parts are really poor quality, or the ones you are replacing are shot, you won't see much performance gain from aftermarket wires. You might see a reduction in radio noise, but I challenge you to find a dyno run where somebody installed new OE wires and then swapped them out for aftermarket wires and saw a performance gain. Same goes for caps and rotors... There just isn't much that can be done technology-wise to improve these things.
If you want to improve ignition system performance, get a new cap, rotor and wires (not necessarily aftermarket), a high performance drop-in ignition coil and fresh plugs. The best performing plugs will vary from car to car... In my experience, Hondas seem to perform better with plain old NGK plugs than Bosch platinums.
thast true, some cars run like crap with certian plugs while others will run like a champ... i kno the s-10(2.2L version) runs like crap with every other plug besides the AcDelcos...