Why proportional representation was not adopted for Lok Sabha?

I. Difficult for the voters to understand the system due to its complicated nature and low literacy rate in the country.

II. Proportional Representation system is ill suited to Parliamentary system of government, since it causes the fragmentation of Legislature into small groups. Consequently, the Parliament would be divided into small groups, which might withdraw support to the government if something, which displeased them, happened. Thus, it might lead to an unstable government.