Possibly the average Guillow's kit buyer doesn't notice or care much about wood quality or density. From marketing standpoint, anything that increases production cost, for example hand selected wood, needs to be perceived by the customer as a value add.
I'd be curious to know what percentage of kits purchased actually get built, and of the ones that are completed, how many of them are flown. If very few end up flying then factory performance upgrades (contest wood, rubber, thrust button) would be wasteful and could hurt profitability.