I'm not the best shopper and particularly hate buying jeans. I need a new pair and am not looking forward to trawling around the shops trying to find some.
You go into the shop, find what is nominally your size, try them on and they are too big/small/short; get dressed go out and find a couple more pairs. Try the new ones on, find a pair that fit perfectly, go and buy them. Go home wear them for a while and find that they have stretched and are now far too big.
Go shopping a second time buy the same jeans in a size smaller, try them on, which entails writhing around on floor of changing room to do up the zip, struggle to you feet to check them in mirror, they are definitely too tight, but once they have stretched as the other pair did they will be a perfect fit.
Go home, go through the writhing scenario again, wear them around house to get them to 'give' a bit. They don't, not at all, not one iota will they stretch. Second pair of jeans consigned to the reject pile.
Go shopping again, to different shop.......and the cycle begins once more.