Not familiar with the exact sort of King Dick to be found in the toolkit, but as dicks do, they come in all shapes and sizes, as do self-grippy things.
I agree adjustables are undesirable when a proper tool is to hand, but life savers when they aren't (just as slip-jaw pliers can be too). I have a few - American, German, French, British and from China too. Plus a home-made small adjustable made by my old Dad in metalwork class at school when he was about 12. A very small 'bad hammer'!
Not sure either about the trade names on self-lockers, I have only got one that says 'Mole' on it, one that says 'Vise Grip', and a few that are Eclipse, own-brand Sears from the USA, unnamed Chinese, whatever. They are all useful for holding separate things together for drilling, filing, soldering, brazing, welding etc. But spanners they ain't.
Every shed needs a few of these things, even if they are weapons of last resort. Here are some, unashamed as I am publicly to acknowledge ownership!