Earlier quoted context omitted.
That mostly happens when they feel they don't get enough attention from you. Sometimes you really are busy with something else, like trying to prepare food for them or answering messages from your pestering boss. But often it is because you are trying to be clever at HN instead of giving them your undivided attention.
Or when they're hungry. Or over-stimulated, under-stimulated, tired, anxious over something that happened at school, hyped for the holiday season. Guilt-tripping someone who shares that they're not always having a good time as a parent is not cool. Your comment is over-generalizing, and IMO quite mean.
It's not that my kids never are unruly. But I can almost always track it down to some failure from my side. I was too busy with something, or simply distracted, so I forgot to give them their snack in time, or they got to bed too late the day before, or I didn't pay attention when they tried to tell me something they felt was important, etc.
And while I'm aware that my experiences aren't universal. The opposite notion that I often hear that tantrums are some kind of unavoidable natural disaster is even more absurd. Yeah, if I bring my kids to the store at 5pm to buy dinner without giving them any snack, while I'm hangry yourself, stressed, and trying to think of something not horribly unhealthy to eat, they might end up screaming on the floor in front of the candy shelves. But my thought then isn't "why am I cursed with such horrible kids". My thought is "ok, I screwed up today, because this was predictable and preventable, and by now I certainly know better than putting ourselves in situations like this."