First, we're not stealing your password.

Each of us in the past have used multiple GitHub accounts to partition work and personal life, or different consulting clients. I kept them in independent Chrome profiles.

We originally had Ship launch the browser, but it was basically a crap-shoot. I often had to paste the link into a different profile.

That said, you're right. We should allow the option to use the system browser.

From a strict security standpoint though, a malicious native app has remote code execution on your box. It's game over. You're just one local privilege escalation away from complete compromise. At some point you have to trust reputation or never use any software. If this is a concern for you, native apps aren't for you, and that's ok.