How the family unit works

Four of us live in this house. I believe we are made more efficient by having different skills sets.

I cook, shop, do laundry & minor mending, do the cleaning, do the decorating, everyone's tax returns and other finance/admin stuff.

I never do anything to do with the car, anything with computers or the internet or technology in general, anything that needs fixing, anything DIY. Anything DIY is a huge category in this house. The house is 104 years old was lived in by a single family for 60 years before we moved in. So slowly and painfully (expensively) everything has been updated over the years, and not by external contractors but by my guys.

To me it seems obvious that, assuming all areas are covered, you stick to your own specialization if it suits everyone. That is what makes a family unit, or any group of effectively co-ordinated people, more efficient than individuals randomly doing their own thing.

My sons girlfriend comes from a household where no-one does anything for anyone else. She gets really cross when my sons says, for example, 'whats for dinner?'. She doesn't seem to notice when I say to him my brake lights are not working and there is an oil light showing on my dash, which he then sorts out. He even gets told off for giving me his payslips (stashed away for tax return time). My husband would have to have an accountant (and I am one) do his tax return if I didn't do it. He is dyslexic and it is just totally outside of skills range. On the other hand he spend a ton of hours on the sitting floor last week fixing our boiler. If I was here alone then that would have cost me quite dearly.

Basically If i lived alone, and in the past I have, then I would do it all or get people in to do the stuff I cant handle but should we not use our own abilities within the group? Is it sensible or am I being hugely old fashioned?