Confused by the 'di-' and 'ke-' prefix placement in casual speech

I’m a grammar-focused learner, and I’m having a hard time reconciling formal Indonesian grammar rules with what I hear in YouTube comments or street-level conversation. People seem to be swapping prefixes or dropping them entirely in ways that contradict my grammar books. Is there a consistent rule for when these prefixes are considered 'required' vs 'optional' in spoken Indonesian, or do I just need to memorize specific verb clusters?