Ramahs
Fucking Combustion (mostly) Since February 2017
No doubt, it is just that the wood is hard to clean compared to glass.
I just swab it out with an alcohol soaked swab once in a blue-moon, without the intention of getting every bit. A layer of waxy-oil can't possibly be bad for the wood.
I don't worry too much about the wood tunnels on my StickyBrick Hydrobrick Maxx either. I just run a pipe-cleaner through them once in a while if they start to get a bit clogged. the wood seems fine.