I'm all for open access, because I think everyone should have the right to see publicly funded scientific research. But from my experience as a journalist who's written a number of pieces on scientific works it often isn't a big problem. I never had to pay for a journal article to do my work.
Most journals also show you abstracts for free, which are overviews of what each paper says. If you find a paper that you want to read in full, email the author - most scientists are very happy to know that people are interested in their work, so they'll give out copies to anyone who asks.
This isn't to defend the paywalls - I think open access is important. But I don't think the paywalls are a valid excuse for journalists.
http://www.pnas.org/content/111/26/9425.full
Not to say that many/most papers can't be found with a little bit of effort, and I can't really imagine a situation where an establishment journalist emails authors about one of their papers and doesn't get it.
Even if I had the time to read several studies and expertise to understand them, I couldn't afford it. Out of curiosity I just went to the Journal of Nutrition (I know nothing about it, picked that journal randomly) and tried to download one random issue. It was $273. Going to multiple original sources isn't practical for most of us.
I doubt that the typical mainstream journalist writing a popular story on a scientific subject could justify this expense to her boss either.