Greater vaults are not that rare in Normal mode, but in coffee-break getting zero or one per game is not unusual. The main reason for this is simply that the number of levels generated is so much lower; but since the levels tend not to be huge, that also somewhat reduces the number of greater vaults, since there is less room for them.
If the game starts feeling boring, you can dive to 99

That's probably what instant-coffee was born from: me realizing how often I was skipping levels in normal coffee.
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Playing coffee changes the ?Acquirement experience somewhat; in normal mode, you might be tempted to dive to a great depth early so you can be extra-disappointed there. Of course, storing the ?Acquirement at home and forgetting you have it is also a valid approach regardless of game speed.
If you want to really appreciate the upside of Acquirement though, play a Yeqrezh thrall and request lottery tickets upon reaching CL 10