I think it boils down to the fact that when they're young (when you SHOULD be teaching them) it's more work to do so. Having a little "helper" in the kitchen or the laundry room or wherever often isn't really any help, so parents get impatient, figure it's easier to just do it themselves and before they know it the kid is so old they've missed that opportunity to teach them when learning it would have been "fun" and the kid resents the "work" they're suddenly being burdened with. And so the cycle begins anew, this time though it's easier to do it themselves because the kid has never had to help before and is throwing a fit over it being "unfair".
I agree about parents just caving almost instantaniously! I wanted to many times...but thought abought theirs and my future with all the bnefits of their advanced independance...well worth it!