My granny advised me to keep some secret money, I think she would have been horrified if I had thought it was my leaving fund though!?
There were a few years when my DH was the only earner and he gave me housekeeping and an allowance so I didn’t have to keep asking him for money. It wasn’t much but we didn’t have much.
For most of my married life I have run my own business so we have a joint account and my business account ( that’s the one I share with the tax man!).
Luckily I haven’t needed a leaving fund but I do use my earnings for big purchases and if I had to go then I could.
Parents-in-Law. What do/did you call them?