In practical inductive reactance always exists with resistance...it means Z=R+jX....R and X can not be zero....R0 and X0 ..in transformer is magnetising parameters...you can go for equallent circuit transformer expression...
To get the work as transformer (to enerzised), magnetization of core is must.It is a pure inductive circuit only inductive reactance (Xo) would have been considered, but in practice, no core is ideal, and is having loss component(Ro=stamping resistance), hence to get voltage on secondary side,the no load current have two component magnetizing current(V/Xo) is component , lag 90 degree, and ,another in phase (loss or eddy current) component(V/Ro). Total no load current is vector addition of two currents, hence Ro and Xo are always in parallel to applied voltage.