Why instant runoff voting, rather than multi-round runoff voting?

Answer

There are a few reasons why instant runoffs are preferable to multi-round runoffs. The main factor is the cost. Having two or three citywide elections, instead of just one, is quite expensive.

More importantly, however, is the impact on voter turnout. It's hard enough to get people out to ONE election. With multiple rounds, participation will likely decline with each round.