Because the US espouses the virtues of the free market while embracing monopolies. If they cared about dealing with the latter they would empower more regulators like Lina Khan.

Airlines need distribution. Concert venues don’t.

Mid/high profile venues know they will sell out regardless, they can shop around the venue rights to the highest bidder.

Ask yourself why airlines deliberately overbook flights while venues do their best to never overbook events, why are subject to identify verification before a flight, and why you go through the TSA before you board... and you'll start to understand why airline seats are maybe not such the perfect metaphor for concert seats.