painting is basically dead, or in a constantly dying state, our maybe more like a constantly evolving zombie. at any rate, it gets reborn again every 5 or 10 years, so knowing how to make your own paint and other useful arty concoctions is very useful.
people who say you're not a REAL artist if you buy all your supplies and supports at Michael's are elitist douches, but they do have a point. I mean if you're happy to paint a stupid little sunset on a pre-made canvas to hang in your guest bathroom, good for you. Get that somewhat aesthetically pleasing bathroom art. but if you know how to make your own casein using caustic lime that will melt your face off, that's pretty hardcore and most likely you're very serious about making art.
I'm not saying you have to be willing to lose your face to be a real painter, and you don't even necessarily have to try all or any of these formulas, but it's really interesting to learn some traditional methods that were used before we had internet and art supplies showed up at our doorsteps after a series of 5 mouse clicks.
I digress, but I really enjoy experimenting with new (old, rather) methods and techniques. I will probably never make it through all these formulas but, hey, at least I stretch my own canvases.