safari and edge users are a tiny minority. Most security aware people use chrome anyway.

Really, you think security aware people use Chrome? The security aware people I engage with avoid it. The baked in data collection and telemetry are a concern for them. Some of them even remember specific problems, like that time it turned out Chrome was listening on your mic all the time, and sending the a audio back home.

The security conscious people I know use Firefox or chromium.

Of course, your point stands: no one's using safari or edge. :)

You always have chromium also don't confuse security awareness with privacy concerns.

Chrome is more secure this means that you have less of a chance having your data compromised including any and all data on your machine by an unknown 3rd party. Since Chrome's data collection is known it can be incorporated into a simple threat model. You know what is collect and who collects it, most security aware people will be OK with Chrome collecting some metrics that in all fairness are likely to be collected anyhow unless they block every JavaScript and Cookie on the planet, do no use any Google service or a service that uses GA in exchange for not having to worry about their browsers being pwned.

Any chance iOS Safari enables it once Apple opens its NFC APIs in 11?

Haven't used it, but the Soft U2F README refers to a Safari plugin for U2F.