It went like this:
1. OCer could get a Northwood, and overclock it. Said OCer got great value, and pushed the new stuff. Athlon XPs of the time didn't OC as easily. Much like with Conroe, and the A64 X2s on AMD's side, a couple years later, Intel really had a bunch of 2.4GHz+ CPUs on their hands, but sold them at various lower speeds, as well, to make more money, by controlling supply and cost of the faster rated models.
2. Normal person would read all about it, and then buy the P4, instead of an Athlon XP, but never actually overclock it, and effectively end up spending more than they needed to. The additional money went into Intel's pockets

. Quite a few games were significantly faster on the Athlon XP, until the 865,
at stock CPU speeds.
With the 865 chipset, the need to OC to get better value went away, as long as you were getting C or E CPUs,
and the 2.4C was a solid 3-3.4GHz OC CPU. Said CPUs could be bottlenecked sometimes, by the 845 and 848, for gaming and content creation.
http://www.sharkyextreme.com/hardware/cpu/article.php/3261_941741_5/Intel-845-DDR-Chipset-Review.htm
^ Blast from the past, including the 1st year of the notorious Intel-biased Sysmark testing!
I kinda miss the fact that OEM CPUs aren't sold at various outlets any longer. I remember back during that time you could opt for the boxed retail or a non-boxed OEM chip without a cooler, which is usually what I chose. I wonder what prompted that change....I still don't think many people use the stock boxed cooler with the unlocked chips.
Counterfeiting in 3rd world countries, by relabeling, was a major problem, through the early 00s. A slower CPU would be repackaged as a faster CPU. In AMD's case, this included changing multipliers.
That led to making it harder to easily buy unboxed and tray units, to multiplier bridges being hidden, and to OEMs actually
desiring locked CPUs (if someone bought 10 Athlon HP or Gateway machines, overclocked them, then resold them as faster, even though the OC was unstable, that made HP or Gateway look bad, in the eyes of the end user). Shady PC shops and distributors were a problem. The unlocked chips, now, are there, or not, for marketing reasons, though, as both AMD and Intel can get a few more bucks for a given CPU.