That's not the only trust model at play. Here is a different example of where FHE becomes very useful.

Cancer researchers will benefit greatly from patient data sets that might include very privacy centric elements such as genome sets, past medical history (of both them and relatives to help understand heredity aspects of the disease). Most people making an informed decision may be uncomfortable with this information being made widely available, at best perhaps OK with a select few groups, but not available to anyone researching this domain.

FHE would solve this, the data can be made available to anyone with compute power that wants to help, while still respecting the privacy of the patients.