I believe this thread is pretty representative of most of my friends and myself in terms of split of chores and childcare.
An extreme example : One friends DH refuses to use his holiday time to cover childcare and uses his bonus to buy new cars, whilst hers goes on family holidays. Thankfully he now seems able to do bedtime, which was a problem for him for a number of years. Meet him and he seems like a lovely bloke, but I couldn't be married to him.
Or another one, I love SIL to bits but am dreading going away on holiday and sharing a property with them again which we are due to do soon. Why? Well her adult DH and grown up adult sons do nothing to clean up after themselves and preparing meals, setting the table and clearing up is viewed as women's work although not stated as such. I was in tears with DH as I didn't want to cause a ruction within their family dynamics, but being female myself felt I was ending up doing a lot more of the work than I should do, because I didn't want SIL to have to do it all. To be fair to DH he picked up his share and I think chivied along my adult nephews a bit.
In my own case DH is lovely and kind and nice and certainly talks a good game about equality. He also works longer hours than me so it's natural that I should have a greater share of the housework and child rearing - he does more of the paperwork. However it is me who is always the one asking about homework, making sure it happens, making sure the gerbils don't die of starvation and making family plans.
DH and I were totally equal when we met, at that time we both earned good salaries and had a cleaner in twice a week so there was very little to do so it was totally equal. A combination of our family earnings going down due to working p/t ( through personal choice as I like to spend time with DS before we go down that particular thorny road), much more needing done as bigger house, DS at school and doing activities and finally a precedent being set when I was off on maternity leave, means that I now do the lions share of it and probably a little bit more than is fair, even when the part time aspect of my job is taken into account.
I don't believe it's because I'm stupid or I married the wrong man. I believe it's down to the above set of circumstances and also a bit of unconscious ingrained thinking that deep down, this is the way things are.
Threads like this are helpful as they force you to challenge your own assumptions - I got DH to make dinner a couple of times last week as a result and made sure I was out doing the car MOT on Sunday so he got DS ready for rugby and made him his lunch as a result. Managing to keep any gains are relentless as the default position is now so ingrained, but worth it in the long term for our marital happiness.