The problem is the same one that Medium will likely soon find out.

The news market is a heavily competitive one, with hundreds of sites offering everything for free with ads. As a result, most people just don't see the need to pay for news. They can find the exact same information in a million other places, and the friction from going from 'free with ads' to 'pay for content' is fairly considerable.

It's like trying to sell a smartphone app. The pressures against it are considerable due to the race to the bottom and a large percentage of people just don't see the point in paying.

So it's a business that's hard to build trust in, requires a decent amount of marketing/awareness, will attract a far smaller audience than the free sites and ends up being a difficult one to monetise properly.