They are taking 3 rounds as that is their process and they are wasting the candidate's time unnecessarily even they know that candidate does not fit for the role in first round.

Conducted 5 rounds of interviews all technical . Coding,algorithms, logical reasoning,soft development methodologies etc. In manager round I was asked to write code in java, I told I am python programmer and would write the same in python. After that round, manager said we want some one who has hands on experience in Java and our HR will get back to you. I anyways got my result there ,but I have no where mentioned java in my entire resume,hope they should have done proper screening or filtering before calling me and wasting my entire day.