Sadly, for them "it's just business" means that their monthly rent is probably $20,000 so for them to give you a show, they need to feel confident that they will make (nett to the gallery) at least $20,000 from showing your work... otherwise there is soon no gallery at ALL. So making a show for a "known" artist where there is already a following of collectors who'll pat $5 for maybe 10 pieces in a month is a much lower risk... that has nothing to do with "how good" you may or may not be.
New artists launching to "sudden fame" is rare... it's more like "winning the lottery" than it is "working your way to the top." Everybody wishes for it, but it's not a realistic objective to plan your life around.