People keep track for lots of reasons. To hold themselves accountable, to measure calories, to measure nutrient intake, because they have a pedantic streak a mile wide, so they can look back and see what worked. There are ways of calculating calories you need if that is your thing. You can go the learn the correct principles and play it by ear route too.
I've done both. It is a pretty good idea to keep a log for a bit. Then you learn your habits and what foods are best value.