What’s worse than a last minute cancellation is when they are a no-show. What I’ve learned over time is that a person’s actions when dealing with plans run the full spectrum and not to take it personally.
My sister is much like you. For the first twenty years of her marriage to a man that was never on time. After getting fed up with her complaints, I finally told her that people are unlikely to change this type of habit. Her frustration and nagging over this was the definition of insanity: doing the same things over and over again and expecting different results. She now takes a separate car to parties and vacations. She has realized that, despite being married to him, he is a separate person, the scowl is gone from her face, and her friends and family accept both of them for their differences.
For the habitual last minute cancellation abusers, they know that it irks others. Most likely, there is a degree of underlying embarrassment about it, whether it shows or not. If it is a friend, you can always cut them out of your life if it is that bothersome. In a work environment, it isn’t that easy.