Possibly because it was offered first and doesn't use the Chrome web Store. At the time the site mentioning it used PeakD which requires your active key, which we new people back then were told not to give out. So some veterans in help, told me to use Hivesigner to avoid having to give PeakD my active key.
I was astounded that you couldn't login using your posting key, so I never use PeakD.
I'm also leery about something like keychain, "holding" my keys as Sam Stonehill got hacked when I first joind Steemit, so I try to be careful.
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