First of all, these are the people who usually have no clue. They tend to be chubby moms because its an easy exercise and looks like it does something for your waist.
Abs are made in the kitchen.
Weighted stuff has the potential to make them "thick" since you are building the muscle and not "spot reducing". I've also never actually "felt" anything from them. My oblique work consists of oblique v-ups, hanging side crunches, some broom / trunk twists, but given displaying abs & obliques is part of bodybuilding mandatories, I practice the shit out of vacuums and an interesting variation of ab contractions w/ a single grip on the lat pull down and some weight like 40-60 lb. Its very, very mind-muscle oriented.
And I agree - full-body stabilization exercises are less dramatic but more productive - planks, side planks.