Seems like they insist on mobile numbers, and that is a piece of data I am not willing to share with the public or Google.
Several people I spoke with were surprised to hear about Google enforcing the disclosure of phone numbers.
-I have now tried creating accounts several times, from different browsers and via different internet connections (mobile, work, home) and always got the same result.
+Google themselves say on their [help page](https://support.google.com/accounts/answer/1733224?hl=en) that submitting a phone number "is optional but highly recommended".
+That's a lie: I have now tried creating accounts several times, from different browsers and via different internet connections (mobile, work, home) and always got the same dialog asking me for a phone number, with no way to skip.
I even tried a friend's computer who said he just recently created an account without having to give a phone number.
-I am not sure what kind of profiling Google is doing here, but I was never able to skip the phone validation step.
+I am not sure what kind of profiling Google is doing here, but they seem to have some kind of heuristics for whom they ask for a phone number and whom they don't.
I am considering various options, including getting a cheap prepaid SIM card just for Google.
All of this may sound somewhat paranoid, but the point I am trying to make is this: at some point we have crossed the barrier where having a Google account was optional.