Benefits of low-profile tyres?

What are the benefits of using low-profile tyres on larger alloy rims? I can understand that alloy rims can result in lower total rolling mass, and therefore - in theory - providing a better result for the suspension by decreasing the outboard mass. But is there really a benefit of using the very low-profile tyres, as is frequently done on top-of-the-range models of many cars? It seems to me these tyres are likely to be more expensive to buy and replace, more susceptible to damage in harsh situations, and with the associated higher tyre pressure, giving a firmer ride. So, is it purely cosmetic, or are there some other real benefits?