Good for developers, but no necessarily end users. Even if you intend this only for development purposes, or for technical users, without doubt, some developer

Good for developers, but no necessarily end users. Even if you intend this only for development purposes, or for technical users, without doubt, some developers will ship their integrations to non-technical end users with instructions to: log into the dev portal, generate a token, add the token here, upload certificate, etc, etc. As simple as that is, it causes headaches non-technical users, which will end up in the support queue. Hence OAuth. But now you have an easy way, and a hard way, and the easy way is how every developer will begin their integration. You'll need to incentivize, or gatekeep, in order to have them complete their integration with OAuth.