The 2000 calories a day is based off a USDA food consumption survey. Ie people self reporting what they ate (and according to a google search http://www.foodpolitics.com/2011/08/where-did-the-2000-calorie-diet-idea-come-from/ the reported numbers were rounded down significantly to end up at 2000).
I’m a big fan of the calorie concept being abolished personally. I just don’t see how it can help when the body can adjust its needs so significantly depending on what/how much is consumed. It makes me think of the futility of trying to negotiate with an infant: your logic, no matter how correct can have no impact on a system that can’t understand anything past its basic biology.
When I first started I had never deliberately restricted my calories but I tracked for a few days and found I was nowhere near even a conservative estimate for a pregnant woman of my activity level. I struggled to consume more until I discovered that drinking calories (primarily whole milk) was an easy way to bump my calories without reducing my appetite.
I’m now mostly just trying to keep my brain out of the way and listen to my body. It’s been 7 months now since I tracked my calories and while I’m kinda curious I’m leaving them out of sight with the scale as a tool that can be helpful, but can also be harmful and I’m personally feeling better off without either.