people need a certain amount of access to liquid assets. Having even more of your wealth tied up in a very illiquid asset may not be ideal, if a time comes when you need cash. Paying 2.5% to have more liquidity is extraordinarily cheap.

Then there is the opportunity cost of what you could do with the extra cash, if you invested it wisely. You'd have to consider risk as well, for sure, but many investors would jump at the chance to borrow cash for 2.5%, which they could then invest elsewhere.