why do aftermarket alternators not work?

I was wonder this while lurking this forum for the last couple of years?
I was thinking that it has to due to the volts? Is this correct? It seems like all the aftermarket alternators I bought for other cars only put out 13.5-13.9 volts out of the box. when I check my rodeo's alternator it is puting out around 14.2 volts. Does the rodeo's pcm need the higher voltage to work?

If the volts are the issue why doesn't the aftermarket put different voltage regulators in that regulate more volts? It seems to me that the rate of return to the aftermarket on this models alternator would be sky high, indicating that the aftermarket is not rebuilding them right?:rolleyes:

Any thoughts would be appreciated! Mike

I think it has more to do with the rebuilding industry. I've spoken to a tech who deals with rebuilders first hand, and he says they often just spray the brushes with cleaner, repaint some parts, sandblast the casing, replace only the worst worn parts and slap it together. Most vehicles are not as finicky as our isuzu's so often it works out fine. This is a case, where it is less costly for them to take back a defect, than to build in that extra cushion of quality and durability in each and every rebuild.