There are two reasons for doing this
The First reason is ola autos charge fares according to the kilometers you are traveling but local normal auto drivers ask the amount according to their localize fixed rate
And Second reason is Ola is trying to make their customers habitual of using their services. So Ola charges a lesser amount than normal autos because people will prefer Ola autos when their rates are lesser than normal autos. This stagey of making customers habitual of using their services is followed by many big companies.