Not many people are actually 6'+ tall. It's around 15% of white men and 10% of the world's men in general. However, a lot of the people below six feet are still very close to it. 5'10" and 5'11" are extremely common heights for white guys (and I'm assuming most people here are white so other white people are their frame of reference). And with good posture and the right shoes and hairstyle, every 5'10"~5'11" guy can claim to stand 6' total, and many will.

If your eye is accurate enough to only pick out people who are actually taller than 6' and not register anyone shorter, then it'd look like a small chunk of the population. However, if every guy has good posture and gets a 1 inch boost from shoes and another 1 inch from hair, you would also count every 5'10" and 5'11" guy as a six footer, and when you do that, it looks like a solid majority of modern men lucked out and not just 1 in 6.