Ticketmaster is a company which is so hated, people ascribe their success to malice and illegal activity rather than any compelling economic arguments. It's unfortunate because their business model is, imo, quite interesting.
The first thing to point out is that the question itself is flawed. Ticketmaster has a number of competitors (StubHub, Eventbrite, AXS, Seatgeek). Nevertheless, artists do seem to always gravitate to companies like Ticketmaster, even when neither they nor their venue have any affiliation.
What we should ask is what problems a naive artist would face selling their tickets like any other commodity:
- They overprice it: No one shows up, people are angry at the artist, the artist is in debt to the venue for overbooking.
- They underprice it: The tickets are hoovered up by scalpers who capture most of the ticket's true value, fans are disappointed they can't attend because finding a ticket is much harder.
Ticketmaster's (et al) primary service is to capture as much of the value of each ticket as possible (through phased ticket rollouts, faux-sellouts, variable pricing, attendance modelling, etc.) and package the event wholesale for the venue and artist. Both parties are can be guaranteed of some portion of the event before tickets even go on sale and the risk for them both is diminished.
Obviously I'm not trying to say Ticketmaster is all sunshine and lollipops, but if you want to make an argument about Ticketmaster's success, saying that they've cornered the ticketed events market globally is ludicrous.