macos – Must we use ssh-agent nowadays?

In the past, I never had to use ssh-agent and everything worked fine.

But I noticed, on GitHub, it is asking people to use ssh-agent, even if we don’t use it, it seemed fine. So I just ignore that lengthy part usually for the ssh-agent and ssh-add.

But for a few days I was able to log onto Bluehost, but yesterday day I added a new pair of public and private key to my MacBook Air M1, and now the log in that used to work becomes:

Received disconnect from 162.241.123.123 port 22:2: Too many authentication failures for mike123
Disconnected from 162.241.123.123 port 22

but it was strange why when it let me log in, it asked me for password, when I thought the whole idea of ssh is not requiring password.

But today, it does not even ask me for password but spit out the message above.

However, my MacBook Pro was able to log in, even though it is asking for password.

The Bluehost tech support was saying, I should paste my private key to their Bluehost SSH panel. But I thought we should never give out our private key.

So must we use ssh-agent now? What might be the issue of “Too many authentication failures for _____” and how is it solved?