How many ICOs "advertise as being sure to appreciate"? I've looked at like 40 different ones, bought into none, but none of them promised any return on investment. That's some straw man argument.
It's guaranteed scarcity. By design. All you have to add to that formula is the idea that there's a demand. And that's what every ICO is: hype about demand for a decreasingly available thing.
Once you have been sold that there's a demand, the appreciation is guaranteed by definition of what it is.
Please avoid making generalized statements, especially ones that are flat out wrong.