What would be the downside?
I guess if you imagine bike riders tend to be shoplifters, you wouldn't want to have one. But I have not seen any reliable stats suggesting that to be the case.
A desire to discourage young people from hanging out near your establishment might be another rationale. But again, that seems iffy. What about adult cyclists with cash in their wallets?
Is it the expense? The space it takes?
Yes, that is former Talking Heads front man David Byrne with a rack he designed.