Can you imagine how much fun that would bring if you could design your own IC and just hit print, then load the die into the carrier and solder the pins?
There isn't even a service like JLCPCB where you could get your custom ICs made and shipped to you.
But in general it’s a very difficult process. The cleanliness required, the scale at which all this happens, etc. are just orders of magnitude harder than a regular PCB. That’s not even considering the nasty chemicals needed to etch silicon which are way worse than PCB etching chemicals!
Lithography requires a lot of space and clean rooms.
The technology is insane, the design skills are non-trivial, and the software is terrible