I don’t think it’s only that, but in many Western European societies (and those derived thereof) it would have been unusual to have members of a family with surnames spelled differently, even if only the suffix.

So the whole family may just have taken the male head of house’s surname to avoid problems, or even been simply assigned his surname by immigration officials.

Many a name were changed at Ellis Island, for example.

Good point. I think Russian surnames are the same right? (Ivanov/Ivanova etc.)

Is it common in these cultures to use surnames as given names?

They did not necessarily forget the rule, it’s just inconvenience, especially when dealing with official business, when you have to explain why (for example) your kid’s last name is slightly different than yours.

You'd think so, but Allison is firmly in the girls camp today, at least in the US (Liverpool FC's male goalkeeper Alisson Becker is Brazilian). Madison is also more associated with girls.