Yet, a somewhat sizeable category of people still invest in gold ...
Could it be that the definition of "investment vehicle" is broader that what you may have willingly restricted yourself to?
What? Gold us physically useful and relatively scarce, THAT is why it has value.
You are acting like people just got together and said "hey, let's take this useful hunk of garbage and assign it some value to see how rich we all are".
Correct. Gold's value in an industrial sense is no different from any other relatively scarce material. This is precisely why gold is not an investment. Its value is simply a group of people assigning a value to something driven in part by scarcity.