Once there were components which are very Large and Heavy...(Like Hardisks and other components) Now there are so many are put inside a tiny block. But why only a few processors can be put inside a block now. Why not thousands of it inside? What's stopping us?
Depending on your definition of a "processor", GPUs are already there. The RTX 4090 for example has 16,384 processing units. The problem is, GPUs are only good for well structured programs, something that a typical user program is not and cannot be for various reasons.
This is also in addition to us wanting more and more functionality out of general purpose processors. We could probably fit 1000s of general purpose processors into a single unit... if we were willing to use an 8-bit or early 16-bit CPU core from the 80s.