I posted about my dislike of calorie counting as a approach to diet.
But it's not all bad for a diet.
By the way, I say "diet" for a reason. "Dieting" is restricting yourself to lose weight. A "diet" is a collection of foods that sustains your life over the long term. I dislike using the term "dieting" - in fact, even when I would cut weight I just told people "I've adjusted my eating plan." With a goal to being 179.9 on a given Friday weigh-in for grappling or 83 kg on a given Sunday for MMA, but still - a change to my eating plan.
Anyway, back to calorie counting.
When do I find it useful?
Spot Checking - Writing down all of your food, logging it, and totaling your calories over a few days is a great way of finding out what you're averaging. If you need to add about 500 calories to gain weight, know what that is.
You can use spot checking every few weeks or perhaps 3 days in a row once a month or two just to ensure you're still getting the food in that you want.
Although people trying to lose fat hate to hear this, I mainly used calorie counting the other way. I logged my food for a few weeks as I added more and more when I wanted to come up a weight class. I eventually found I needed close to 5000 calories a day to put weight on and keep it on. 5000 day in, day out. It was work because it's hard to get that much food in without excess fat, without junk, and without liquid calories (I can't tolerate milk, and most of the others are junk.) Without spot checking, I wouldn't know if I'd made my numbers or where about my numbers needed to be.
Establishing a relationship to food amounts. Write it all down, check the totals, and know that what you ate. So if yesterday was 3000 calories and what you ate that other day was only 1800 even though it felt like more, you know that.
It lets you eye food and have an idea what it will mean over the long term in your diet. You know what 1000 calories of chicken and pasta and carrots looks like, and what 500 of it looks like. Even with errors creeping in, you're in the right ballpark.
What I think that's superior to the daily count: you don't get caught up in "50 calories under today!" or "I better eat 100 more calories!" or "I'll swap 300 calories of chicken for 300 calories of beer and I'm okay!" nonsense. You get an idea of what you need to eat, and then move on and get on with eating that.
To check your macros and micros. A good food logging app or website will tell you what percentage of your calories come from protein, fat (and what kinds), and carbohydrates (and what kinds.) You'll also get a total of your micronutrients, or at least the major ones. This can help you identify deficiencies and over-abundances. Still taking that C supplement but you get in 750% of the RDA? Not eating calcium-rich veggies but you're getting about 80% of your goal for the day? Good to know, and logging in an app is a great way to find out.
Setting a basis. I do this with my clients when they ask, and I've had it done with me. You use a calculator to establish some basic caloric needs. You set some ratios for macros. And then log for a few days to ensure you get close to that number.
That way, you can see what 2750 calories or 1800 calories or whatever looks like, and check to make sure your chosen foods dial in the macros you want.
In those cases, I find calorie counting pretty useful. As a diet strategy, I find it weak. As a tool in an overall diet strategy, to build and reinforce that plan, it can be a good tool.