Depends. I'm not sure you could make a business out of just fixing monitors. As another thing the phone repair shops can fix - maybe?

As for why? $ per benefit.

I had a pair of Samsung 204B screens I liked. I didn't see dollar per benefit in upgrading from 1600x1200 4:3 to 1920x1080 16:9.

They went funny, I obtained a capacitor, pop the back off, unsolder and solder new cap, put the shell back on. Job done. 20 minutes per screen because man, am I bad at soldering...

They worked happily for another 5 years each. Until society got well past the 1080p rut and into proper 1440 and 4k etc screens which were actually worth upgrading to.

Edit: make shorter

1920x1200 in 23" or 24" were an OK upgrade from 1600x1200 CRT 21" for me. I did the stuff you did on an 18" 1280x1024 SPVA LCD from Fujitsu-Siemens. Since I hadn't soldered for a long time, I just bought that stuff 2 times, because the parts were a few cents only. Didn't need them 2 times, though :-) Worked for some mainboards in similar ways. Except I've been afraid to completely desolder them on mulitlayer mainboards, for fear of destroying the VIAs/through-holes. Just pulled the capacitor from it's pins still stuck in, cleaned them, and soldered the new one(s) onto the old pins. Looked like sort of a water tower in miniature, but the boards worked flawlessly afterwards. For years :-)