There's reasons behind this. LPDDR IIRC works most efficiently when it's closer to the CPU than what dimms would allow for.
Boosts speed and lowers the power requirements.
It also incentivizes people to buy larger SKUs than they originally wanted, which, bluntly, is probably the main driver for going that direction.... I'm just saying that there's technical reasons too
Don't forget, food and shelter. Pretty sure that was free too