The idea of smaller meals eaten more frequently comes from bodybuilders or anyone trying to build lean muscle mass. One of the key things revolving around this is that stimulating the maximum effect of protein synthesis tends to cap out as early as 25g in the meal, maybe up to 50 in some people. That is, if you eat 80g of protein in a given meal, it doesn't have much more effect on the protein synthesis rate, and the only mass-building benefit you're getting out of it is the number of calories in it. Therefore, since protein is far more expensive than either carbohydrates or fat, it makes sense to only eat to that 25g-30g level or so per meal. But, if you want to hit a good overall daily target of both protein and total calories, this necessitates that you have to eat many more meals throughout the day.

It's fine to use as a weightloss strategy too, just dropping the total daily calories ingested to below maintenance level. Only drawback is that for people who have been overweight for a long time, i.e. non-athletes who aren't used to controlling their calorie intake, it's easier for them to consume too many calories per day through the frequent eating. You have to be pretty regimented because even an extra 50 calories per meal on that kind of setup can blow any deficit you're attempting.