They're...limited. I think the potential is there, but you'd need Rune Sages and engineers to find the best way to harness and manipulate them. It's like having several different kinds of gears and levers that each only have perhaps four functions each; you still need to actually put them together and find the right interactions to accomplish an equivalent. I can't conceive how you would replicate, say, the functions of a phone solely from those pieces. Or a computer, or an arcade machine.

Which isn't to say it can't be done -- but it would require a lot of ingenuity, and specialists who were looking to make some extremely specific things happen.