Why? Because the thought of leaving them in wee is horrid
I also don't encourage them to just wee/ poo if if they can do elsewhere. How hard is it really to take baby out bath, dry, and pop on toilet before adding nappy? How hard is it to put them on the toilet at every/ most changes? How many people only change 3 times in 24 hrs, then go onto the other mn boards at complain that their 3.5 year old is still not dry.
It is laziness. We used reusable nappies and wouldn't have dreamed of saving washing by leaving more. Just mentioned to dh and he said that in his opinion it's the same as leaving a baby covered in vomit or not feeding when needed.