Odd, really. I agree with all of you!
But if pushed I tend towards not using 6 min/ XX mile markers, at all for my students. I certainly don't use them myself.
But just to be curmudgeonly, they ARE definately useful to 'ingrain' the concept of TIME as the initial identification indicator.
Still, I'm quite sure most relatively experienced pilots DON'T draw 10 mile / 6 min markers - instead using the time to the next most suitable navigation feature.
As CFI indicates, it's precious little use to have a marker (in miles or minutes) that doesn't have a terrestrial feature to match!
------------------
How surprising! Aircraft use the same laws of aerodynamics all over the world. Has anyone thought to tell the CAA?