Money and games people want to watch, either at the ground or on telly, and follow ball by ball on the radio. Give the punters what they want.
As for standard, it's cyclical. I don't know when this summer's tests were arranged, but it wouldn't surprise me if it had been pencilled in 2 years ago when England were still beating the Aussies in the ashes and challenging SA as the number one test team.
Yes it is cyclical. But whereas SA and Australia oscilate between being the best and say 4th at worst, we rarely trouble #1 and are usually at 3 or 4, sometimes a good deal lower. Australia were probably at their poorest in that fairly recently series in Aus where we beat them 3-1, and I reckon they were 4th best in the world. Even if they were 5th, they hadn't been anywhere near as bad as that in 30 years. Our cycle takes us back to that standard in less than half the time.