Question

why intrensic semiconductors are not used for making electrical devices

Answer 1

Because it isn't doped = insulator(just lower energy gap). No free electrons ,so it needs to be excited to conduct.

Answer 2

@catch.me

That is not the correct way to put it.. cause in that case i can ask.. why can't we use conductors which have tons of free electrons? :P

Answer 3

@Mashy
Yea use it in which kind of electrical devices .If you want to make fuse , you use conductor and if you want to make diode you use doped semiconductors.If you want to isolate something, you will insulator.If you want to use low break down voltage, you use pure semiconductor as it is lower than insulator.
It depends on the goal of making this electrical device(why not conductor??) .