DDR1 and DDR2 were clocked 20x and 10x slower than DDR5. The CPU cores we have now are faster but not that much faster, and with the typical user having 8 or fewer performance cores 128 bits of memory width has stayed a good balance.

If you need a lot of memory bandwidth, workstation boards have DDR5 at 256-512 bits wide. Apple Silicon supports that range on Pro and Max, and Ultra is 1024.

(I'm using bits instead of channels because channels/subchannels can be 16 or 32 or 64 bits wide.)