[valarauko]

It's not a perfect system, but the provisions of the Anti-Defection Law tried to address what was a bigger issue in Indian politics - legislators changing sides for what turned out to be enormous sums of (undisclosed) money. In this climate, the incumbent party could bribe opposition members to prop up the government, and attempts to poach new legislators right after the elections reached ridiculous levels.

For what it's worth, while this does hinder a legislator from voting as per the will of their constituents even where they are at odds with the party line, within the Indian political system there are so many special interest parties that differ from each other in minor details of policy. In theory, the will of constituents could have been made manifest by voting for the policy adjacent party instead.

Again, it's not a perfect system, but it's attempting to fix the obvious issues that arose in India.