As it is, those get funneled off earlier in the process, and people get annoyed.
And I really don't get your example with credit card fees. You're suggesting the credit card processor not collect the fee at the point of sale and instead send all the money straight to Swift's bank account and then expect her to turn around later and cut a check? How is that more efficient than just having them collect their fee at the point of sale? It is just shuffling money and complicating it unnecessarily.
And once again, would most artists really even want to personally get involved in handling all the mechanics of who pays who when and how? I doubt it, they'll once again probably just contract that part out as well. They have a lot of work they need to do as the performer to get ready for the show. So once again it'll still just be some middleman they hire to do all this financial plumbing.
I agree, it looks like there's a certain level of monopoly with TM/LN in this space, and it sounds like artists pretty much need to take the whole package or none of if the artist wants to play at major venues. Maybe allowing these things to split up and be a bit more competitive will reduce prices, make things better for the artists, or whatever. Maybe forcing these people to separate just creates more friction and it gets harder to put on a big show or ends up more expensive overall.
In the end, these middlemen will continue to exist in some form because they do provide value, especially at the scale of putting on a show for many tens of thousands of people.
In general the public doesn't like how the sausage is made, and if you reveal parts of the making they get angry about it - even if everyone involved basically agrees it's for the best.
(Ask the random Swift fan how much the A/V company is paid to manage the equipment and they'll probably be off by an order of magnitude or more - the most famous example of this kind of thinking is "I can make eggs at home, how come a restaurant is so expensive?")