Let me put it this way: computing is evolving in a way where SMALLER registers are actually more important for new types of algorithmical necessities. AI/ML is a great example - you have to program in specialty frameworks such as CUDA or Tensorflow which want to have registers as small as 8bit so that things are done faster, in the GPU or in L1/2 cache. The hardware of GPUs for instance is made with 8 and 16b logical processing units in mind.

Larger registers only really help a portion of computing, while you can emulate the odd large register you may need without affecting performance THAT much with a combination of smaller registers.