On creating a new Gmail account, they first asked for all the details. I didn't add my mobile number as I did not want to give it away and left Current Email as blank. After agreeing its TAC, the next page asked for a mobile number. It was This page. They have this on their support page :
Why Google asks for your phone number to verify your account?
In an effort to protect our users from abuse, we sometimes ask users to prove they’re not a robot before they're able to create or sign in to accounts. Having this additional confirmation via phone is an effective way to keep spammers from abusing our systems.
Note sometimes, but I get this same step every time I create an account. Earlier this didn't happen on my iPad tablet. Doing the same on my PC doesn't get to that page asking for the number.
So what criteria makes them ask for number in some devices and not in others?
How to bypass this?
I have read How can I get around giving my mobile phone number to Google? but my concern is based on devices used. This pops up only on my iPad tablet and not on my PC.