Well from my view as European working in finance. Handling money for customers to pay (buy apps) likely requires an e money license (not sure about other states). And with this there is lot of things coming, like AML and what not.
So disabling the account might be due to regulations required for the e money license.
Of course Support should be able to resolve this if proves are given
It is probably lazy in the sense that they would need more lawyers and more careful ToS. Defending their ability to shut anyone off completely is a lot easier than dealing with lawsuits from customers denied X, denied Y, denied Z in regions A,B,C..
Gift cards are often used for money laundering or scams, because they allow to transfer monetary value in small increments and without tracking: there's no link between the person who bought a gift card (anonymously with cash) and a person who used its code to put money onto an account.
Of course Support should be able to resolve this if proves are given