That assumes that we have enough RAM to hold all of the data we could ever want to analyse and that we have this data at startup. Neither of which has ever been the case as far as I have personally experienced.
The response time is quite fantastic (less than a minute), but there are drawbacks: - GC takes in the order of minutes to complete - loading the data takes 90 min from spinning rust
So yeah, it's possible, but your bottleneck becomes the storage driver.
Source: I work at SAP's internal cloud team. For our internal customers running SAP HANA, we offer baremetal machines with up to 6 TiB RAM.