Their is because you need skill for depth and depth being important for more higher mu ores etc not to mention working the system as ma has always said it's dynamic so some days stuff will drop others it won't plus add fact certain stuff can be found in certain areas at certain depths.Let's look at the skill involved to mine, pick a spot, drop a probe, if you miss, you either wait 15 minutes and try again, move on, move to another server or alt f4.
If you hit, extract it and move either 108 or 110m, drop probe..
I used to think there was more to it than this but I was sadly mistaken...
PE had a better mining system than EU.
Theirs a hell alot more going on then you mention for instance theirs massive holes in places because bulk general players are using either terra 8s with d class and lvl 5s which leaves pockets not to mention you have the big server refreshes that happen twice a day? I could go on but the information is out their although I have a slight different theory with depth being alot more important then just better chances mu ores.
Everyone has their own theories but way you should be mining for optimal mu is unamped it's tedious slow and I think a well known experienced miner said they make 25ped a day from it for 7 hours work.