Serving remote desktops to several hundred developers. Maybe a video content server for a netflix or youtube type business. Hosting a large search index? Some kind of scientific computing?
Numeric simulation (HPC). Some, not all, simulations need lots of memory. In 2018 larger servers running such had 1TiB, so I'm not the least surprised that six years later it's 16.
We don't see more of these machines because most tasks are better served by a higher number of smaller machines. The only benefit of boxes like this is having all of that RAM in one box. Very few use cases need that.