GRF Spec extension impedance mismatch
In no particular order
* not many devs familiar with grf spec
* so designing and reviewing can be hard
* some of the requests are misguided
* interacting with newgrf authors can involve blah blah politics
* but sometimes multiple misguided requests point the way to one solid spec extension
* nobody writes nfo any more, so very few grf devs actually understand the action0/1/2/3 spec, even less 6/7/9/D
* nml is easy to patch, but the inertia of having both patched openttd and patched nml is high
* maintaining wiki docs without fragmenting wiki docs :(
* getting test grfs is a PITA (see 'nobody writes nfo any more')
* testing some grf features requires savegames, but these break frequently due to openttd / grf changes