Micro.blog is the only service that I use which uses email-only authentication. And it is a win-some-lose-some experience. There are times, especially on mobile, when I love that there is no password involved. I open the email in my client, click a link and I am in. But then there are times, especially when I am on a system where I just don’t want to login to my email, I would prefer authenticating via a device I own, I trust - usually my mobile.
On IndieAuth front, I completely agree with Glenn. It is wonderful to login with your own website.