Question

why do we use soft iron for making an electromagnet and not steel?

Answer 1

because steel is not a good conductor of electricity

Answer 2

Hi,

We use soft iron for electromagnet because we wish to make electromagnets temporary magnets i.e. they should be magnetic as long as current passes through the solenoid wound around them and become demagnetized when no current is passed. 

Soft iron has low retentivity thus they lose magnetism when current stops flowing.

But if steel be used then it will become permanent magnet, i.e. it will still remain magnetic even if the current through the solenoid is switched off.