Easy, because if you walk back just a few years, there was no 35mm option. Medium format has been at 39MP since at least 2005, something that 35mm only hit with the 5Ds/R and A7rII only hit in 2015.
Those same advancements in 35mm CMOS tech applies to the much more profitable MF range, thus the 33x44 50MP Sony chip, and it's 100mp sibling. To go further, the high-MP 35mm cameras are greatly impacted older lenses, where you really have to have the latest glass to get the best results. Medium Format glass covers a larger area, allowing for larger photosites, and while the latest lenses really are needed with the 100mp chip, the quality of the Zeiss Hasselblad V-mount glass works great with the current 50/60MP digital backs.
There are trade offs, but everything is. My use cases are for images that are huge, where folks can get right up to it. I'd either have to stitch a lot of 35mm shots together, or do a single/few shots stitched in MF.
Now my question for you is did you shoot any MF film in those 30 years? Really, take the time and rent a RZ or Hasselblad V or even pick up a Bronica setup for a few hundred dollars. Shoot a few rolls of 120 and tell me it doesn't put a smile on your face when you look at the negatives for the first time.
-Joe