Fill form from identity

New to Bitwarden. Testing it on laptop with Firefox browser (with security options set on very high) and on Android phone app.
Filling forms from identities works marginally on the laptop. It fills some fields, but leaves others unfilled, like the city or last 4 of social. Tested this on several different “create account sites”.
On the phone, its worse. I have not gotten it to fill one single of these “Create account forms”
Any ideas why this works so poorly?

Yes, it really depends on the site. My experience has been a lot better than yours, but I have had less than perfect results many times, too.

If web designers standardized their forms better, I am sure it would be an easier task for the software. Otherwise, the BW client has to make a good guess - if the team ever improves this feature, what I would like to see is some form of a learning algorithm where the detection of fields gets better over time as the user corrects what BW guessed at.