1. They give men a pancake-butt. Enough said. Stop reading if you are easily offended.
2. They do not flatter your stuff.  I'm not even going to delve into this point, for the obvious reasons.  All I'm saying is that the puffy front of dad jeans makes your frontside look airy like a plastic grocery bag.
3. The high rise or long zipper creates a really unflattering midsection. The worst is when the rise hits at the smallest part of your waist. The best rise is below the natural waist, at the hip-bone.
4. Dad jeans NEVER appear long enough.  It's because they are narrow at the ankle to the point where they sit on top of your shoes.  Jeans should never be more than 1" off the ground.
5. Consistency of color.  The wash of "dad jeans" is usually a consistent, all-over, dye that fits the name "blue jeans" to a tee.  It's extremely outdated.  Jeans are no longer called "blue jeans" for a reason- they come in multiple shades, colors, and tones!  Unless you are 50+ you really need to jump on the bandwagon that we call "distressed denim."
6. The seams are lighter in color because the dye wears off.  No, this doesn't count as distressed.  The unevenly faded seams simply create an ugly distraction from the rest of the jeans.  Check out Obama's example of faded seams below.
7. "Dad jeans" are not cheaper.  You might feel like all other styles and brands of jeans are going to be more expensive than your good ol' trusty "dad jeans."  Well, you're wrong.  Nowadays, you can get flattering denim at any price point (from $10 to $100).
8. Tucking a shirt into "dad jeans" is the ultimate failure.  I would rather see you forget to wear underwear than to make this mistake.  Tucking your shirt in is really dated.
9.  There are only two directions for "dad jeans" to go-- either like a toddler with a full diaper, or a 40 year old virgin.  Take your pick.
10.  They give you a wedgie.  Dad jeans look like they're riding up, if you know what I mean.