when you buy perishable food, you sometimes won't be in the mood to eat it before it goes bad.
when you serve yourself a plate of food, you will sometimes put too little on the plate and get seconds. so too will you sometimes put on too much and throw the excess out.
when you cook, sometimes you will mess up, and the food will turn out gross.
some food you buy just won't be very good quality (like some fruit that turns out mushy or not sweet)
sometimes you won't read the labels closely enough, and will buy the wrong food by accident
sometimes you will make food for someone else, but because of miscommunication it won't be wanted.
sometimes you will start to cook some food, then change your mind about what you want to eat.
when you buy more than a bite of something new, you may not like it, and would thus throw most of it out.
the error rate on all these things goes down with skill. thus younger people, esp young children, tend to have a higher rate of throwing food out.
this is all to be expected. you shouldn't be upset in the slightest if 10% of the food you buy isn't eaten. more if you are young, or have young children, or have many children.
and none of these things qualify as "wasting" food.