Sorry for the cagey title, but I've got to use euphemisms for the problems with this style of underwear.  To put it bluntly, men's pouch-style underwear is supposed to securely cradle and contain you.  There's an access flap for use when you go to the bathroom, but it is not adequately secure when you don't want to Free Willy.  This is an unfortunate defect that requires too frequent adjustment and re-packing to be comfortable.  When underwear fits correctly, you don't even know it's there.  This style reminds you with each slip of the flap as you transition from the soft cotton of the underwear to the rough denim inside your jeans.  It's unpleasant and distracting.  Perhaps their flap opening is too large or the fabric of the "tuck" is too stingy to overlap far enough.  I use to wear Munsingwear underwear all the time in my youth.  Perhaps as an adult now, the ...ummm cut is no longer consistent with my needs.  Most likely, the tailoring of these briefs is now being done somewhere in Asia where the fit may be different.  In any event, these will not be suitable for many guys.