Vanity.
Though I can only eat about 1000-1200 calories per day, about 75g of protein. I am STUFFED with this amount. I've been eating this way over a year, stats are:
5'8. 18 inch neck, 45 inch chest, 17 inch arms, 31 waist, 24 thighs
So measurement wise, I've actually lost zero inches going from around 3500 calories to 1000 and 200g of protein to under 100g. But I do look FLAT, a lot of the gym regulars have commented how much size I've lost. Which is odd that I measure exactly the same but shirts and everything fit noticeably bigger.
Inches mean nothing. Gauge results off body fat and lean mass measurements. Your shirts likely fit bigger because lean mass has been replaced by body fat, which is softer and doesn't fill out clothes like muscle. Nobody drops their calories and protein by that much and doesn't lose muscle, even the genetic elite would.