Leaping to Primera's defence I have noticed from further research (I must be bored today!) that mid range fares showing on the .co.uk website do include a meal and bags, and buying those fares does appear to come out somewhat cheaper than taking the no frills fare, then adding the stuff you want - assuming you want to take a hold bag and have some sustenance during the flight.
I guess they're hoping people will click on the basic fare because it's cheap, then not realise they could do a better deal taking the higher fare with many of the add ons included. Perhaps not a bad business strategy, but I'm sure some consumer groups would whinge about it being underhand / unfair or whatever else.