Part of it is due to my overall ignorance when it comes to fashion - I love clothes, but I like shopping on the cheap and definitely don't keep up on my Chanel and St. Yves Laurent (if that's even a thing) or what ridiculous get-ups are draped over models on the catwalk (they can pull off anything... I can't).
Another reason I've avoided skinny jeans is because many of them simply don't fit. A while ago, I found a great chart that evaluated your measurements - and it kindly informed me that my ankles would only be proportionate on a woman who stood over six feet tall. Many skinny jeans in my size, even some of the stretchy ones, literally will not fit over my monstrous heels because the bottom hems don't have much give.
Both of these obstacles could be overcome... there definitely are skinny jeans out there that would fit, and they've become so pervasive that you can pick them up at K-Mart and wear them with any shirt on the shelf. The real reason I persist in my mom-jeans is psychological.
There was a period of time, when my family lived in a ridiculously big house we couldn't sell and my family was trying to pay two college tuitions (both mine and my mom's) when we didn't have much money. As a result, I was dressed mainly in hand-me-downs from relatives and the bounty from an occasional trip to DI. When I was 14, I owned three pairs of jeans, and all of them were skinny jeans. Today, this would probably be fairly normal. In 2002, back when Britney was still all that and most teenagers didn't even text, wearing a pair of skinny jeans was something only women over 35 attempted. Any passer by could have seen that I must be wearing clothes someone more sensible had rejected, and I was painfully aware of it. Shy 14 year old girls don't tend to excel at "working it" in "vintage".
When our/my money situation changed, I loaded up on flares and gave those skinny jeans back to DI. Unless you count weak moments in dressing rooms when I've temporarily thought about giving in to the trend, I have't been in a pair of skinny jeans since. My past experiences being unfashionable have scarred me to the point where I now insist on being unfashionable. My main consolation, besides how awesome it is to wear skirts and not have to worry about pants at all, is that at some point bootcuts will be back and I'll be the hippest 30 year old mom around.