I think some people interpret 'flattering' as:
'Doesn't accentuate the bad bits' (which a tent that barely touches any part of your body definitely does does achieve).
Rather than:
'Accentuates the good bits and hides / deflects from the bad bits, so as to make me appear an improved version of myself'. This will be different for every shape and height.
And yes, there are clearly people out there who don't seek out 'flattering' clothes, but the fact that you've bought such a bandwagon item, that appeals to you, and you (presumably) feel good in, belies that.
Nobody's going to spend money on - and wear - something they actively think makes them look bad.