The attack scenario here is malware on your computer pretending to be a hardware authenticator (during sign-up or 2FA enrolment) but really just emulating one in software.

Is that extreme? Yes, but the upside to giving out attestation data just isn't there in most scenarios. It's like I have to step over broken glass to get a stale bagel. Yes these boots mitigate the risk from the glass very well but I don't even want a stale bagel anyway.

There are some scenarios where attestation makes sense. If you issued every one of your employees a genuine Yubico Yubikey then I guess it could make sense to insist on checking with attestation that nobody is using some homebrew device they built instead. But for general use? Even the tiny risk isn't justified, so it should be "off".

Here's someone much smarter than me proposing something you could do if you really care about the features from attestation but don't want people to give up privacy. If you insist on offering stale baked goods, here is how to clear up that glass:

https://www.imperialviolet.org/2019/01/01/zkattestation.html