I'm an electrical enginner, still studying, but close, plan to go into local area network engineering, but I deal with consumer electronics day in day out, they're not like cars, where bugs are fixed through the years.
Electronics usually function flawlessly before mass production, via simulations and such. Then the sample production units are beaten to hell under loads of stress, overvoltaging to detect tolerances, exc. Then, the first verions go to the customer.
After a little while, the manufacture decides to make more money (or save some as they look at it) and manufacture a 'compatible, alike product' by cutting a) quality control b) quality of components c) alterations to design to save costs or d) all the above.
Usually D, especially the case of Playstation, PS2, XBOX, DVD Players, various computer products such as CD Burners and especially devices such as cell phones and pagers.
Sometimes, products even LOSE features through this phase. Example: XBOX's manufactured after December 2002 now have ONE cooling fan, not TWO. One fan cools the CPU and GPU, not one for the CPU (also exhaust) and one for the GPU itself. ANOTHER Example: PS1 1001's had RCA and Parallel output, 5xxx series, the next in the generation, lost the RCA outputs and then needed a proprietary (expensive at the time too) Sony AV cable. Then, the 9001, last of the PS1 (not PSone) line, lost the parallel port too, not to prevent modding, but to save money on making internal traces and a connector.
Need more examples? Look around your house at ANY electronic. It's equivilent 5 years ago had BETTER quality control and better choice components, and probably functions the same or better than the newer generation model you have.