Not true, from the FAQ:
How do I withdraw money I have received?
You need to have a valid bank account associated with your profile. You can then request a withdrawal. This works worldwide as long as your bank accepts international bank transfers.
It is quite hard to make money with Flattr (you need to be really popular to get enough micropayments), and I guess that 95 % of Creators never reach the 10€ limit to actually withdraw their money. So giving money back to others is the "obvious" thing to do.
So, just shuffling money around is neither the obvious nor the intended solution.