Hi! Founder of Evervault here.
You're totally right in saying the number of developers who are actively integrating encryption is pretty small as of today. What we're trying to do is improve developer experience to a point where encrypting all sensitive data is a no-brainer. Still early days here, but we're expending a lot of energy to make this happen.
Re: third-party dependency — we think the same way at Evervault. We bring third-party vendors into the mix if we think they can build something better than we could do ourselves, which is why we partnered with AWS on their Nitro Enclaves[0] product. Our root of trust is the AWS Nitro System. For customers who still aren't comfortable with us managing their security posture, we also offer on-prem and in-VPC options.