In the UK - no. My current salary is fine. A larger salary implies more work/responsibility/hours, a larger percentage will be taxed, and if I don't like it I can't easily go back. I can also be fired more easily in the first six months of employment.
Actually it’s 2 years. The probation periods don’t have much grounding in anything. 2 years is in law. (It’s a common misconception that once you “pass” “probation” that you’re safe)
It's written into my contract, so I get a larger notice period and potentially redundancy money if I'm fired after six months.
I haven't studied the actual law, probably should!