You are correct. But the construction cost of these is dirt cheap. I have bought similar non-movable models from Chinese companies for about 2 dollars. These ones are priced at 10-20 times as much but the wood and cutting quality is more like twice as good.
Though I wonder whether one can reduce parts wear somewhat by painting the wood with something.
I tried waxing (just rub with plain old candle) the sliding surfaces, it helped a bit but didn't last long. However the wax helps during assembly, putting tight joints together.
Though I wonder whether one can reduce parts wear somewhat by painting the wood with something.