On the railway side of the ticket barrier, you’re thinning your potential customer base from ‘everyone in town’ to ‘rail users only’, which in practical terms restricts you to ‘food on the go’ operations.
On the public side of the barrier, many stations suffer from not being located in the traditional shopping areas of towns (which are themselves in decline), and the Victorian premises are not what retailers are looking for - the fit-outs would be complicated. I can think of a few stations where professional service firms (local accountants and surveyors etc) are tenants, in office use, but I’m guessing the passing rents are very low because poor quality office space is in over-supply.
Then there’s very niche retailers like the coin and medal emporium at Bromley North, who must rely on a combination of low rents and equally niche customers who know where they are, because there’s little passing trade.
The way to make money from property at larger railway stations is to knock down what’s there and build residential towers, which would be well-connected by public transport. But mention of re-development and ‘greedy developers’ sends people apoplectic.