That is not the point. Something needs to act as a deterrent so teams don't go into debt.
Even in real life, business transaction accounts earn you jack all in interest, next to almost 0 due to the high volume of transactions on these accounts. Whereas if you go into an overdraft, you pay a large amount of interest so people don't overdraft if they can avoid it.
This game is not about investing your money in a term deposit for 6 months for interest!