There are a few reasons for eating only once a day as a monk. Making yourself easy to take care of is one of them, as you mentioned. But there is another interesting point that a senior monk taught me while I was ordained. He said that one of reasons food intake is restricted is to avoid building up a lot of energy reserves which often leads to getting your mind going on the wrong things, something that's particularly likely with young men who haven't reached an advanced level of practice. Among the many precepts for monks are restrictions on movement like running and climbing. So the monk's lifestyle doesn't lend itself to burning off extra energy.
Along the same lines, monks begin to gather energy through different methods. They aren't eating as much but can sustain themselves off the vitality of the sun and surrounding environment (if they are in a clean, restorative environment.. basically nature)
