Sometimes it's also because we change as adults and kids lack the experience to properly communicate why they're upset. I remember I had battles with my parent

Sometimes it's also because we change as adults and kids lack the experience to properly communicate why they're upset. I remember I had battles with my parents over certain foods that legitimately tasted awful to me as a kid and made me gag (and then later as an adult some of those foods taste fine). For some kids it's probably the normal tantrum/boundary testing but I would not be surprised if for some kids they have a significantly different eating experience with even something simple like bread crust. Even for adults, consider that cilantro/coriander tastes like soap for some people. And that's just one easy small example where we're pretty sure we know what gene causes it.