That's actually a crucial part of the culture to me - my company does dinner at 6PM, which everyone in the company knows is motivation for keeping people at work until then. I'm very thankful it's not 8:15PM. I don't want to be expected to work late daily and then have it disguised as a perk.
For the US, 6 PM is a normal dinner time, electricity or not. If you're in Europe, I understand where you're coming from. Mind you, that's the start - you can come and get food as late as 8PM if you please. The point is that for the most part, everyone can get their dinner at the time they want to.