It depends what you mean by 'work', OP. Looking after small children is work - if you weren't doing it, someone else would have to, and if that someone else wasn't a family member, payment would be involved. Some activities which are very enjoyable and easy to do earn the person doing them a salary so they are described as work, while other activities are tedious, repetitive, difficult and exhausting to do, such as caring for a helpless individual, and these may not earn a salary - does that mean they are not work?
Yes, caring for your own small children can be fun, rewarding, exciting, heartwarming, uplifting, but not all the time. Really, honestly, very few people feel ecstatic over wiping the tenth shitty arse of the day, or scrubbing mashed weetabix off the kitchen table yet again.
And if you don't have a paid job because you have a high-earning partner but your children are school-age or older, how much of the domestic stuff is your job? And do you ever feel (or get told by your partner) that sex is something you should always approach with enthusiasm when he wants to engage in it, because after all he's paying for your food/shelter/clothing?