First, it's still a problem of finite space. It is not going to be practical to scale out until supply reaches demand in many locations. There are only so many Friday nights in a month, which also makes fungible repeat shows finite, and repeat shows cost time that could be better spent increasing global coverage.
Second, price and venue-filling are signals of quality, so there may actually be some people who do not purchase tickets that appear to be too cheap or do not go because they do not feel invested when the ticket price is low. Then this results in empty seats which negatively impact the artists publicity.
Third, the discriminator when you have a low price point but low supply is the willingness to get in line. This can be a valuable metric to select audiences. Removing it makes it harder for artists to select their audiences.
The set of all people willing to buy at $50 is at least as big as the set of all people willing to buy at more than $50. Demand curves slope downwards. If you supply enough to meet all demand at $50 and price at $50, then everyone who would buy at $50 does and there's no extra seats.