why do people think 犯人 is only for serious crimes

Actually, 犯人 is way simpler than people make it out to be. In Romance languages like French, we distinguish between a culprit and a suspect, but in Japanese, 犯人 covers everything. It literally just means 'crime person'. My textbook says it's only for serious 'criminals' but I've seen it in a kids' 絵本 too. It's just like 'culpable' in Spanish. Stop overthinking it, it's not just for murder cases.