I can understand for some people who can't accept any inconvenience or those who normally buy Volvos and only care minimise any possible risks while on the roads. I used to think that enthusiasts choose a BMW for its mix of handing, road-holding and quality ride as a priority.
To me run-flat tyres defeat the purpose of buying a BMW. I chose to drive a BMW because I want the best motoring experience without any compromise. So that means the best tyre grip, and low un-sprung weight. Perhaps BMW are following changes in the market... IOW, people have gone soft!