In what scenario would one want to use this tool? It would seem to make less work, but the upshot is, of course, that you don't know what configuration options will be used for your kernel, which could very well mess things up.
The messing things up is the point.
It's used for what's called "fuzz testing" - making sure the kernel config can't be put in a state where the kernel can't compile. Rather than rely on pure human ingenuity to break things, they enlist the help of entropy.