Ahh this age old debate! I've seen many photographers who don't require food and couples who don't think they should feed their photographers, all with good reasoning (some are budget, some are special food requirements) however, see it like this. The photographer/videographer is that one person, that one supplier, who will be with you for most of the day. In fact, besides your family and friends, they are most likely to be the only supplier that is with you from getting ready right to first dance and beyond. And if your wedding day is anything like most other couples, then that's a 10 to 12, sometimes 14, hour day! Not to mention that we provide you is one of the few items from the day that will last for pretty much ever!!
To feed your photographer isn't a legal requirement as we don't have a union like bands do (can you believe that it's legal to feed the band, even though they're only there about 4hrs and after dinner time which they could have had at home!) however it's really most appreciated and helps us to keep up our energy. Yes, we could take a sandwich or salad, but have you ever left a sandwich in a hot car all day and then eaten it? It's a soggy horrible mess and there aren't many foods that outlast the heat or last the day and still taste nice.
It doesn't have to be the same meal as the guests which I know is expensive, just leave a tab behind the bar and we'll have a chicken burger or something, it just needs to be a hot meal. You can ask the caterers for a suppliers meal too. Most meals are served long after we start (I recently did a wedding where I didn't eat for 10hrs as I had breakfast at 7am before I left, and the food was served at 5pm) and I bring snacks to keep me going, however, that hot meal gives me the energy to keep going into the night.
And to be honest, it's just an appreciated nice thing to do! It shows that you care about your suppliers, and yes I know you're paying them, however, these people put a lot of heart and soul into the day, not to mention hours of work before and after the big day has come and gone, and I can tell you that if you show care and compassion it will go a long way to getting more from us! I recently stayed almost 2hrs past my leave time at a wedding because the couple welcomed me so warmly and made me feel like I was appreciated rather than just there to work.