Why do I feel the need to say thank you??

Yesterday, whilst at work, the same old question arose - why do i feel the need to say thank you? To my husband that is! He started his facebook day off with the status update ''I have already clothed and fed two children, emptied the dishwasher and made dinner''......this was at approximately 10.30am. I read it rather bemused. I had been up with Chloe since 7am, had managed to clothe and feed her AND myself, and gotten ready for work and out the door by 8.25am! My reply?? ''Get a grip!'' The updates went on for a little while, amusing our mutual friends no doubt, and more importantly - amusing me!
So when I arrive home at 5pm, with dinner cooked, and husband busily folding clothes in the backroom, I have to stop myself from saying thank you. Why? Well, because I always used to say thank you, but over the last few months or so, have ceased this due to the fact that I don't get a ''thank you'' at the end of every week day. He returns home from work to a cooked meal, bathed and fed children, and a pretty much organised household! Although I know he appreciates it, there's no thank you. Just the same as he goes to work five days a week and earns a decent pay packet to make life easier - but I don't thank him for that either!
I'm wondering how many other mothers/wives out there feel almost obliged to say thank you to their husbands when they do things around the house un-prompted?

So my quote for the day - ''The smallest act of kindness is worth more than the grandest intention''. ~Oscar Wilde. Just as I do everyday things that I know will make my husband happy, I'm hoping this was his intention too! Have a lovely day!