A few years ago (circa 1996) I had the good fortune to be employed in a lab that had a low-energy, high-current, ion implanter. One of my tasks was to keep it operational, but It mostly stood idle since the people who actually used it to dope semiconductor wafers had long before then moved on to greener pastures. Not once did I ever consider using this machine to make my own transistors... or anything else for that matter... even though highly purified, grain-oriented, monocrystalline silicon wafers were readily available for literally pocket change.
I did toy with the idea of making micro-electromechanical systems (MEMS)... tuning forks, microphones, rate gyroscopes, sensors on itsy bitsy cantilevers, etc. Soon gave up that idea when I discovered I could purchase ready-made stuff right off the shelf at affordable prices. It just got better and better after that.
Being able to build integrated circuits is like having a license to print money... assuming you can come up with the initial billion dollars or so to build and staff the fabrication facility. Next best thing is being able to rent time in such places to become a fabless manufacturer of integrated circuits. Third best thing is being able to purchase integrated circuits for a few hundredths of a cent each in large quantities, provided you don't have a Not-Invented-Here (NIH) mentality. For those that do have a NIH mind-set, there still remains ASICs, and microprocessors with program protection fuses, and field-programmable logic arrays (FPGAs). But make your own transistors from scratch? Not in the 21st Century.