Why does an artist need to be well known? Maybe they are a young and new artist, who becomes famous after they die. IDK if the artist is well known, all that matters is if I like the art.
Because of precedence, lowering the risk of decline of the price. Not saying one should choose only on price, but if one is going to buy art anyway, why not think both ways? Something you like -and- something that more likely will increase in value. There sure is enough of it out there.