Case in Point:
In my latest game, just as I got to the point where I needed Glassware/Sand, a Trader came by with 400 Sand for sale.
Bought all of it, of course.
As of this morning, 16 GAME-YEARS LATER, not one grain of sand has been offered for sale through the Trading Post.
Nor has a single shard of Glassware.
The 400 Sand ran out long ago, and luckily, since this is NORMAL for the 500+ hours I have been playing this game, I had started terraforming a vertical-sided mountain to get to the only Sand deposit I have found on this map - at the top of the mountain, of course.
My Tier 4 housing, without glassware, would have devolved without access to that deposit, and the 3+ years it took to carve the mountain into a flat top and roadway to the top to get access.
Since then, I have found another regular Sand deposit, at the far corner of the map where it will probably take a second satellite village to provide housing for the workers in it., and a regular stream of carts to get it back to my main Town.
In other words, my only choice is to either ‘rely’ on totally unreliable Traders or go through major construction projects just to get access to a single Resource which is Required to get to Tier 4 Housing and stay there.
My experience has been, through 3 towns to 1000 pop and another 5 - 6 to Tier 4 but lower populations, is that Sand is the scarcest resource on a Lowland Lakes map. Back in 7.5 to 8.2 I regularly got Lowland Lakes maps which had only 1 small Sand deposit or none until you explored the far corners of the map, as far from the notional ‘start position’ as it was possible to be.
Now, I can accept that as just the ‘downside’ of Lowland Lakes - every map should have one except maybe ‘Idyllic’ - but don’t go telling me that I can always use the Trading Post to get around map resource limitations, because that is flatly contradicted by all my experience in this game.