You're idea for a universal login is amazing. Here's why: people who login with steem account could maybe use a version of the website with upvoting, and currency transfers.

This would allow people who like the concept of steem and like being rewarded for comments have a steem login that works everywhere, while users who don't want to transition to this system keep their website as it is.

I imagine this needs lots of work to get done and needs approval of the websites where it is used, but it's doable long term.