I would say several reasons ( though these are not for me
)
1 - cheaper than a V8
2 - better fuel economy
3 - not everybody modifies their car for racing, some people like low/mild power
4 - why drive a Prius when you could drive something with similar fuel economy and the looks of a Camaro?
Does not mean I think like that.
But some people do. And if there is a market for it, why not make a car for it?