While I'm sure they are sitting on piles of DRAM, the chances are it isn't DRAM you would actually want; knowing the average OEM's terrible part selection mostly driven on what's cheapest today.
Hell, an awful lot of OEM BIOS don't enable XMP or equivalent by default, if not missing the option to change the setting entirely.
This is of course not a new phenomenon. Commodore were notorious for modifying their systems to accomodate whatever chips were cheap on any given day. Some variants being rather survivable than others.
Unfortunately in consumer-land, I would never expect average joe to be able to discern the difference buying good kit makes. If they could, certain outlets would be long since bankrupt.