Death and artists.

Van Gogh, Francis Bacon and other artists became more famous after their death. While some of them had recognition during the lifetime, it seems that death has some sort of auto-advertising effect. People tend to pay attention to people either when they're dying or dead. Isn't that quite ironic? I am sure Van Gogh or Jackson Pollock could use some more support during their lifetime, but it seems that it isn't so. Do all artists, in order to be valued, have to die first?