Most of it just comes with the territory for provincial clubs, I'd say. Most journos work in cities, so inevitably it's that bit easier them to focus on the clubs in those cities.
It probably doesn't help that with one domestic exception, Motherwell haven't actually achieved much on the park in many of our lifetimes that anyone other than ourselves will still be talking about in another 20 or 30 years time. Whatever you think about them still banging on about it, Aberdeen and Dundee United really were among the best teams in Europe for a while when many of us were growing up in the 80s, so even now they're just going to get a bit more favourable attention on that basis.