I don't believe these super high levels were ever contemplated in anything approaching an original plan.
Personally of I were new tomorrow, and I got to say TM lets say L50 XP 55215, and started to look at the game a bit more, and found out L100 (top irons) came in at a cool XP 2,268,312, hmmm what to what to do?
Been a real trudge to L50 I would be thinking, and do I want that 4.5 times trudge, and possibly more by then? Reality is I would probably looked at things before that, but kept it conservative.
I am guessing WGTs view is the vast majority do not ever look at things like that, and just treat it as a casual game. That's why we get nonsense like the CC Event which is their endeavour to appeal to the broadest spectrum. leave aside arguments over good or bad that's the point.
L90 on is probably showing to be too small an area to really target resource to grow it, simple as that.
All that said the ? remains is XPs 1,800,000 (rounded) a sensible gap between L90 and L100. Part of the competing the mental side after all.
Personally I think that's a rotten carrot if one at all, and more a levels system not designed to work that far. IMO they need to at least create other routes for keen players to get things moving a bit sooner / hang around in CCs but it is WGTs game and their resources..........Can see how that wait sucks if you are a genuine player keen to try and compete with the big gun, and that's just understandable human nature.........
EDIT: Don't forget there are many ways to get the pro shop open a bit earlier. L85 / 90 irons etc are way loads to get TL (even properly), and way loads to play courses real well. In my view you need to be more than an orange tee TL to even care, and if some mark was put down (not elite but tough enough) that allowed the pro shop open a bit earlier if you hit that mark (real tees SP) then great carrot - would not matter to anyone else as clubs won't be that difference anyway. If it were not for time and scared to make a change (program wise) it's a no brainer IMO.