The semiconductor processing for high-end DRAM is not the same as for high-end CPU logic or cache SRAM, so it is not cost-effective to put both on the same chip

The semiconductor processing for high-end DRAM is not the same as for high-end CPU logic or cache SRAM, so it is not cost-effective to put both on the same chip. This was a recurring obstable to past processing-in-memory R&D projects. To mix the two for thermal reasons would lead to some crazy multi-chip modules as in the "chiplet" approach reported recently. However, I suspect you would need far too many chiplets and too many bonds to really give you this thermal benefit rather than just having individual chiplets which are still hot spots with problematic cooling.