1) To sell. (ie make money, to buy food, shelter, clothing, time share condos, girlfriends, etc)
2) Social recognition (which is another pathway to food, shelter, girlfriend's pants, etc)
The "artist" that creates, but doesn't show it to anyone, has a mental disorder not conducive to survival.
Well, all the above is disproven by the cave paintings in Northern Spain and Southern France. Who do you sell a cave painting to? The caves were so hidden that it took thousands of years to find them, so who was he showing up for? No one.
Further, many people paint and do artistic things for the pleasure of it. Some women knit, sew, some men do things from wood and other materials. They do it for the pleasure it gives them, not for profit and not to satisfy any material need. Mankind is the only creature that does this.