Ticket retailers are both a monopoly and an oligopoly. Essentially all retailer has a monopoly over a given venue. The venue may be allowed a small amount of ticket blocks which are used for their own purposes (direct sales, gifts, charity, marketing, etc..) but the vast direct-sales come through a single distributor.
Those ticket distributors are largely an oligopoly, since venues only want to deal with reputable outlets with large market shares in order to maximize sales.
All of them (Venue, Talent, Distributor) have a very shaky interest in eliminating scalping at all. Tickets are sold, the stadium is filled, most people are happy. Scalping only hurts one group of people: Consumers. In the long long term, people will be so jaded with going to 'ticketed' shows that the attendances will drop below capacity. That also hurts the smaller acts far more disproportionately than the rich ones (which have a more captivated audience to saturate the scalping tax). The arts dies and we all point fingers at one another instead of 'fixing the problem', whatever that looks like (I've given my 2 cents in a different post).