Gainsborough Lea Road is about 1 mile walk away from the town centre, don,t think thats a busy station either.
Almost 142,000 in 2014-15. that comes out to almost 400 a day (so 200 on, 200 off)
I think that is a remarkable usage, given the distance from the town centre, and the miserable Sunday service. (A bit of a drop cf 2011 figures, when it was 154,000, which is roughly 3,000 a week.)
Indeed, at nearly 22,000 popn, Gainsborough is larger than I thought. I suspect its main traffic flow is towards Retford and Sheffield.
The problem with trains using Central station (approx 1,300 pax per year) is - what service would use it? Not much chance of Nottingham - Mansfield - Worksop being extended that far, and it wouldn't really do the job in any case. If Robin Hood Airport were to take off, could it justify a Doncaster - Gainsborough Central shuttle? big if though.
In any case, it would need turning facilities to be installed beyond the station - I don't suppose they come cheap.
All in all, as far as passenger rail is concerned, Gainsborough is just not in the right place!