People are giving them everything. Their thoughts, feelings, intentions, company IP... It's a fucking gold mine.
There's just too much value in retraining on that data and even if there wasn't, the feds lean so heavily on Google search histories to get convictions I am certain there will be pressure to prevent any mass market services from adopting this.
This is the same kind of thing. The crazy overhead of FHE means it's not practical for almost any kind of real world computational work. But having it available at all is undeniably technically impressive, and some of that sense of technical refinement bleeds over into your opinion of Google as a whole.
Incidentally, being a business client of Google's who actually uses this (or, say, quantum computing) for $BUSINESS_FEATURE would garner the same kind of positive attention, independently of whether it's technically a good idea.
Finally, if the overheads come down to the level where they are still significant but not insane, GCP is in a great position.
Not that I'm a frequent customer, either before or after.
But at the same time HE is classic Google promotion fodder. Really difficult technical problem! That’s what gets people promoted at Google. Nobody actually cares about it or will use it? That also is what gets people promoted at Google. Because Google only employs “the smartest people on earth” which means people who solve difficult problems. Difficult problems - not problems that need solving.