because, other than by reading my site in my sig:
A) SOcket-thermistors do not measure solely CPU temp. They measure socket-temp, socket-air temp, heat coming from the mb, and CPU pcb temp.
B) The results are almost often compressed versus core temps since it is a secondary heat pathway measurement, and one that is uninsulated
C) certain heatsinks designs tend to "manipulate" socket-thermistor readings for the "reading benefit". A popular example is the thermoengine, when looking at overclockers.com testing the Thermoengines end up wiht far lower socket-thermistor readings than other heatsinks, but has similiar heatsink-thermocouple readings as the others. Therefore, when relying on socket-thermistors you get a false sense of performance from this heatsink. And no, the thermoengine is not the only case where this happens.
D) Thing such as fans on the heatsink are blown out of proportion when using socket-thermistors. Again going to the Overclockers.com testing, when they switch fans, the socket-thermistor shows a good 33-50% more gain in performance than is actually realized by the heatsink-thermocouple. Again a side-effect of being a secondary heat pathway measurement nad one that does not measure solely CPU pcb temp.
The result of that is when upgrading a fan, you get more air blowing on the MB, which definately effects socket-thermistor readings, which is why you see more benefit than you would actually get in core temp.
E) Socket-thermistors, for these reasons and because they under-read core tmep and are useless for testing heatsink grease and can overexagerrate some heatsink and fan combo performances, are utterly useless for heatsink comparisons.
Mike