Same idea as 0% balance transfers that were quite common several years ago, which was also at a time when 5-6% checking account returns were common. People made very tidy sums by taking huge amounts of 0% cash and just sticking them in high-yield checking accounts to make no-risk cash.

Those days are over, in any case. Yeah, you can make a few bucks a month, but nothing compared to ~5 years ago.