It can depend on several factors, for example, if the spouse was Executor he may felt there was no need to apply for probate, then something cropped later and that he found he needed probate after all. If a house was involved, it depends on how they owned it, or there may have been a problem with insurance.
If someone else was Executor, there may have been a reason they couldn't act immediately, there are all sorts if reasons for delay.
When my husband died I was his Executrix and because everything was owned jointly, Probate wasn't required. Then an Insurance Company refused to pay out without Probate, it was only a small policy taken out when he joined the Army as a teenager, but it was in his name. The Probate Office thought the Company was being unreasonable because it was a small sum. In other policies taken out later I was the named beneficiary, so they were not affected.
When my mother died, I was the Executrix and sole beneficiary, I had no trouble with a different Insurance Company who paid out without a quibble.
