Yep, that's part of the economics and politics. Currently it's not really the NHS that makes the dietary recommendations, although they'd provide input. And of course end up responsible for any consequences, ie coping with increasing diabetes and obesity. On the politics side, governments have a variety of policy levers to play with, like the recent sugar tax on drinks. And there's the bigger ones, like agricultural subsidies and production or import quotas. Some of those are currently under the EU's control, and changes may get opposed by agribusiness and junkfood suppliers.
Then there's safety or lobbying around possible new markets, ie objections around US chicken imports because it's washed in chlorine. That aspect may be hyped, ie US does it to reduce contamination and salmonella, and the chlorine content in the wash doesn't seem that much stronger than our tap water. I think there are far better arguments over other practices, like the safety of antibiotics and other drugs used to maximise production. Again though that gets very political, ie US-China's trade spat affected US pork exports and got modified quickly after a bit of lobbying.
Then there's consumer education. So buying a bag of ready to eat salad or sliced veg from the local supermarket's a convenient but expensive way to buy veg. Supermarket's are helpful and stick a small cost per kilo lable, but may not be so helpful and flog things like brocoli as a single serving smothered in plastic. Which I guess could also make veg go off faster as it can't breathe. And then there's practical education so people aren't as reliant on ready-meals and have a better idea around meal planning and cooking.
I certainly noticed my shop was more expensive initially, but then switched to buying veg from the local market instead.. Which helps those traders vs the supermarkets. And since becoming a regular and a bit of banter with the greengrocer, I get a few discounts and deals. Which is a relationship that's hard to build with a self-service checkout. I'd certainly eat more meat, if it were cheaper though.