Almost all chip collectors have some microprocessors in their collections. I suspect that most collectors are primarily interested in microprocessors. Certainly beginning collectors start there. Microprocessors are the rock stars of chips. They are the brains of the computer.
Some say they are the easiest chips to explain their function, maybe so. I think the advertising of Intel and AMD have had the greatest impact on the awareness of these kind of chips. Explaining the function of a memory chip is easy. Describing the data paths/widths, addressing modes, address decoding, direct memory access, dynamic address translations, etc. to use them is not.
These chips can do so much, are so complex, and differ architecturally, I find them difficult to explain, once you get past the brain analogy, especially when comparing one to another. I admit I live in the weeds, I know more details than any normal person would want to know, hear. You, however, do not need to be so maniacal to have fun collecting chip (you might check out my page on the types of collectors).