I cycle pretty much past Oxford's Covered Market (down Turl St) daily, on my way home from work, and often want to get fresh vegetables or meat. But I never go there, because there's no bike parking. (Or a few tiny pockets of parking which are usually full and are awkward to get to.)
Similarly, I love bookshops and would regularly stop on my way home for a browse in Blackwells. Except that there's never any parking outside and I don't want to sit in the middle of the junction trying to see if there's any free parking on Parks Rd. (Where about twenty bike parking places were recently removed with no announcement or explanation.)
Any retailers who think they'd lose out from replacing the 24 car parking places in the middle of Broad St with 150 bike parking places are almost certainly wrong. (More plausibly, the car parking should be removed, the carriageway narrowed drastically and the pavements widened, with new bike parking put on the periphery.)
There is a lot of bike parking at the Westgate shopping centre, but on the southern end, behind the car park and difficult to access from most approaches. There's very little bike parking anywhere near the two destinations I visit (or might visit) regularly: the council library and the Sainsburys.