Maybe I've been really lucky in the past, but I've never encountered parents wanting to reduce their hours - until recently.
I've had two reduce their hours by just half an hour in the morning, and I strongly suspect two more are going to try and shave some time off in the morning or evening in order to fit in with their older child's school hours. So not enough to hoof them and replace them, so to speak, but enough to have a financial impact when you add it up over the course of a week.
The other thing that has shocked me, is a total lack of empathy in the way they let me know. My current parents are generally lovely and well mannered, but it's been a case of 'I won't need an 8am start from September because big sister doesn't start school until 9, so I'll just switch to 8.30 starts". Another parent, who is replacing her first born here with her second born in a couple of months proudly told me that she has applied for a part time job, and if she doesn't get it, then baby brother will just do the same hours as older brother. It was only after she had gone that i thought, "Oh, so if she does get it, she will be reducing her hours or days".
There are so many financial ebbs and flows in our profession!