That’s because the artist has to be dead before their work is really appreciated.
Has any live artists sold one of their works for over a million? Don’t know as I’m not really into art, other than the mentioned female art forms.
For an artist to be dead limits the supply.
Without comment on whether I appreciate their work...Rothco, Warhol, Lichtenstein, and many others had works sold for big bucks (not sure about millions) during ther lifetimes. Death does not make work “good” or “important” — it just limits the supply. Lots of artists sell their work for substantial sums, sometimes due to a bandwagon effect, good promotion by dealers, etc., but usually because the work itself appeals to the buyers.