I do not know how to explain it but I found a wonderful answer from Apple Community.
"A debit card, gift card, etc., can not be used to provide legal proof of identity. A credit card can. Because of the laws regarding the use of online services that collect data by children, you must use a credit card to set up Family Sharing. It's a legal requirement so that you can give parental consent for your children to use Apple's services." - KiltedTim
There is no need for a credit card after all. I just share iCloud Drive space with my wife and I don't have any credit card on file, just GC.
I wouldn't say Apple lying about a need for credit card but it's misleading at least. If I knew about this earlier I'd have subscribed to premium One long time ago.