Presumably for chargebacks. They are taking a risk on you, by partially underwriting you. If they did not have a deposit on hand, any chargebacks that would occur, they would not have the means to immediately collect this from you and process it back. With the deposit, this provides a safety net to Braintree.
Why does Braintree require an initial deposit when you open a payments account?
Why is it difficult for merchants outside the U.S./EU to support international payments?1 ansIs there a company that lets you accept bank transfers globally or across several countries?1 ansWhat alternatives exist to 2Checkout for Pakistani ecommerce businesses facing high cross-border fees?1 ansDo U.S. companies use web-based electronic checks, and which payment gateways support them?1 ans