After that, it's going to be "encryption at rest" (if you're storing these lists as part of the service) and then various and sundry compliances. That'll open you to the enterprise market.
The nice part about E2EE is that it makes a zillion compliance issues go away. It's always encrypted at rest. It's always encrypted in transit. There are no DLP issues. There are no data sharing or processing issues. There are no multi-tenant issues. There are no law enforcement data access issues.
(All of those are for sufficiently small values of "no", perhaps literally not none whatsoever, but guaranteed better than if you're storing readable data.)
