I think this is useful for any service, not just throwaway accounts or "low value" services. It provides another layer of anonymity, and makes credential stuff

I think this is useful for any service, not just throwaway accounts or "low value" services. It provides another layer of anonymity, and makes credential stuffing impossible as a hacker would have no idea that two auto-generated emails address belong to the same person. 1password integration is nice, because you don't have to open up Fastmail to generate a new masked email. I just use catch-all with custom domain, though. That way, I'm not tied to a particular provider, and I can make new "masked emails" on the fly however I want (usually, just using the name of the app/website I'm signing up for). The downside is that you loose the previously mentioned anonymity since a hacker could link your various addresses by domain name. But it's still way better than using the same email address everywhere!