Icarus, a lot of the problem is integration. ATC is still at the stage where everything is handled to the lowest common denominator, because that will succeed.
Can you guarantee you'll take be able to take track shortening prior to top of descent, even when conditions are marginal? Can you guarantee prior to pushback that you'll be at the holding point X minutes later?
Even if you could we don't have the system integration to take advantage of it. The problem is we have to formulate a plan many minutes ahead of knowing exactly what will happen. If we don't leave a bit of wriggle room it goes to **** real quick. That flexibility has an overhead.
Creativity comes at the cost of workload - sure I can achieve the triple somersault with pike & other fancy bits but what about the poor bugger on the receiving end who is going under? It's a whole system you need to consider, not just a departure or two. You can't build a system around always achieving the optimal solution.