Conundrum - Extra Load tyres

[Andy JB]

Here's a condumdrum i cannot readily explain is the application of 'Extra Load' rated tyres on Sport saloons.

I've always had the belief that extra load tyres (with stiffer /strengthened sidewalls) were required for heavy or estate cars which could potentially have loads carried above an average weight, which at high speed necessitated extra load tyre sidewall strength capabilities.

So why on most modern sports saloons of relatively light footprints ie below 1500kg require extra load tyres specified as original equipment? In view of the extra ride harshness these tyres present (similar to runflats) it seems perplexing extra load is required on nimble steeds.

Does this relate to sidewall depression on large rimmed sports saloons and therefore improvement in handling capability while extreme cornering, or simply a commercial exercise to specify the most expensive tyre?