21 years ago, we learned to hate the word "Buffering..."
I'm not convinced how muliticast works to mobile devices, but it's a painfully edge case. This type of event occurs in the UK once every 4 years (the olympics doesn't pull in these numbers -- except for 2012 when it was hosted in London), and even then only when England do well (so once every 20 years)
That said, ITV latency seemed far shorter than BBC latency, watching ITV player seemed acceptable. Apart from the lackluster commentary and the adverts.
And its a matter of complexity - its obvious why OTA would have less problems to solve in order to get the same performance and behavior of something more complex.
IP streaming does actually solve a lot of problems. Plus these days OTA transmissions are all digital anyway. So serving that digital content via the internet is a natural progression. Sure things are superficially more complex at the moment but the technology hasn't matured yet.