It's not as common in the US, since most states are at will, either side always can give notice at any time for any/no reason (other than targeting protected groups / whistleblowing, etc), there's not as much point to a probationary period.
But culturally many companies operate that way. It's easy to fire someone within the first ~6 months; if you've been somewhere for awhile, you give longer than 6 weeks notice; and if you've been somewhere for awhile, you get severance.