Stephen Gould wrote a paper in 1979 that suggested many aspects of natural selection had no apparent reason. Except, he also used words its title that made many an Evolutionary Biologist scurry for a dictionary. A Prime Minister in a Westminster model with a coalition government in a multi-party system appears even closer to a spandrel than a chin does on humans.
The executive powers of the Prime Minister are almost non-existent. The reasonable dispensation that the position has — to hire and fire ministers — is what a coalition set-up takes away. And any other significant policy decision requires legislative backing that cannot really be achieved by the benefaction of the Office of the Prime Minister. So unless the person is also the political leader of the formation in government, a Prime Minister can do precious little domestically. As Manmohan Singh has. This possibly also explains in part why India’s general elections have rarely been Presidential.
If someone is obsessed with the Office of the Prime Minister as much as the principal challenger has shown himself to be in his campaign, does that exhibit the philosophical ineptitude of the candidate or the populace? Or, more worryingly both willing to alter the status-quo of executive authority?