Why cant i buy a 1Ghz/32bit MCU in SO16?
And what's the point in such MCU, what are you going to do with it with given pin count limitation that would require 1Ghz/32bit?
EDIT: that said without mentioning other issues like power delivery/decoupling. Also 1GHZ is not even in MCU league at all. Those SoC chips normally have external RAM and flash, often as second BGA package on top of them.
Sometimes, actually many times you want to compute a lot on a very tiny space, audio one among many apps, serial in serial out on TDM. Other things could be distributed computing instead of one big fat complicated expensive PCB one uses many simple PCB. The argument that just because a MCU is fast it need many pins is inadequate.
Example situation: A mixed signal board, many timers, many uarts, many ADC channels etc, all runs in low power mode slow speed, CPU runs at say 27Mhz all mounted on "single side" (like swear in church) ultra low china cost PCB.
Now you need big fat powerful computing! What do you do? Slabbing on current market solutions is going to ruin the
whole solution so if there was a 1Ghz 32 bit SO8/WLCSP10 MCU (1.34euro) with a serial com's for offload that would be splendid you dont agree? Easier to say no instead?