Add a "for the children" angle and you're ready for congress.
Edit: As far as baseless speculation goes, I suspect it has nothing to do with legal liability and Apple being in a better position to release a Square killer at the OS level.
The App Store exists for the benefit of one organization: Apple. Whether users or developers benefit from it entirely depends on how their goals align with the goals of Apple. It is a very real and stark example of the principal-agent problem.
Your baseless speculation can be disproven extremely simply, and that is by pointing out that Apple would never broadcast a move (such as entering the payment market) by squashing competition, until they're actually ready to announce. Since they're not announcing anything, it's pretty obvious that this is not motivated by squashing competition for anything.
This Bitcoin app was approved long before the recent spike in public/media/government interest in cryptocurrencies, and new ones are being consistently rejected.
The price would be too high - Apple has never paid more than a few hundred million for any acquisition[1] and Square are reputed to be north of $4B[2].
OK, but I still don't see a compelling business reason that having a payment processor would be good for Apple. They can already process payments, how does helping Barbara at the flea market of Little Jim's Cafe process credit cards help their core businesses?
That sounds more like the "Apple should own everything" school of thought. More like what Google or (old) Microsoft does. It doesn't sound Apple-y.
They actually already do this with their retail stores: You can scan products with the Apple Store App and pay for it using your Apple ID and its charged to your credit card on file.
This is brilliant when you're at a mega-busy Apple store on a Saturday afternoon and all you want is a Lightning cable adapter. Pick, scan, pay, show the nice man on the way out, PROFIT.
Edit: As far as baseless speculation goes, I suspect it has nothing to do with legal liability and Apple being in a better position to release a Square killer at the OS level.