https://www.airbnb.com/help/article/1237/how-does-it-work-when-airbnb-verifies-your-identity ([mirror](http://archive.is/DPikR)):

> At Airbnb, we’re always working on making our community as secure as possible for everyone. That’s why, before booking a home or experience, or becoming a host, **we may ask for a government ID** or have you confirm your legal name and add your address.

> [...]

> When you’ll be asked to confirm your identity: This may happen for a couple of reasons. For example, some hosts require their guests to complete identity verification in order to book their place or experience. **There are also times when Airbnb will ask you to confirm your identity to help us make sure you’re really you**.

So unless Airbnb asks for an ID, you're fine.

For the destinations where guests must (by law) share a copy of their passport, you can (always?) directly send it to the host. Examples of such destinations: [India](https://travel.stackexchange.com/q/121398/1810), [Italy](https://travel.stackexchange.com/q/143511/1810), Peru.