Let's say we're living in a world where Apple's IAP framework has a 5% fee. This is roughly in-line with baseline credit card transaction processing fees, think Stripe or whatever, at 3-5%.
Many apps would still choose to not use Apple's system, because of exactly what Match says: Its not a matter of cost, its a matter of power. Service providers want to control the billing relationship with their users; they don't want Apple to have any control, because Apple is traditionally very pro-Consumer, and they will delegate much of that power to the Consumer. Service providers don't want their users to have any power in the billing relationship.
There are reasonable arguments why this is fine; say, for example, a service provider wants to offer some customer 20% off for the next three months, for whatever reason. This kind of setup is hard to model in the IAP framework; its very egalitarian.
But, overwhelmingly, the problem is more-so when it comes to canceling subscriptions, and whenever Match or Netflix or whoever says "we want to be able to directly deal with consumers" you should delete every word they say and replace it with the words "apple makes canceling free trials and subscriptions too easy, and we want to make it hard." There's actually nothing else to it; the magnitude of the fee Apple charges is high (30%), and needs to be reduced, but that tax is dimes compared to the profit companies make from users paying for subscriptions they don't want or need.
So; competition states, if their solution is genuinely better, companies will use it. Actually, this is false; companies don't give a shit about their users. They won't use it, even if its better for users, even if it were free, because the solution is definitely not better for them, because money is power, and Apple's IAP framework delegates too much power to Apple (a third party) and the users. The competition argument is actually irrelevant, because the two solutions we're comparing (self-managed sub management vs Apple-managed) are actually not fungible in the same way Stripe is fungible with Square (or whoever). They carry fundamentally different externalities for both users and service providers.