Not having a browser extension is also a security risk, because copy/pasting is error prone, and does not protect you from phishing - which is more of a risk than someone taking control your computer and bruteforcing your vault IMO (of course your threat model might be different from most users, for example if you store passwords not for the web)
(Disclosure: I work for a commercial password manager that do offer browser extensions)
I agree that there are risks either way, though like you said, the threat model is a bit different. SpicyPass isn't explicitly for web passwords. It's just a generalized key value store with added security. I use it to store my bitcoin keys for example, and that's probably not something you want to expose to the cloud and/or your browser.
With that said I don't rule anything out for the future.
(Disclosure: I work for a commercial password manager that do offer browser extensions)