If it was just a matter of adding more memory people would. A few thousand, or tens of thousands of dollars aren’t much to organisations that have that much data.
The trouble is that there are limits to how much memory you can fit on a motherboard.
And how much you can afford. My partner's scientific research group recently upgraded their shared server used for analysis ... to one with 32 GB of RAM and 8 TB of storage. I think they could have done better, personally, but it's telling how thin budgets are stretched in a lot of real world cases.
The trouble is that there are limits to how much memory you can fit on a motherboard.