By being late, you are being selfish, with the lack of empathy you are being a narcissist.
When you inform the other person, if they are someone who is on time, that you will be late — say 30mins, they will need to readjust their plans. This may mean they will need to find something to slot in the 30mins break. But I doubt you have thought about this because you only care about your own schedule. You simply do not care about the person’s schedule while yours is more important, which is why you are a narcissist.
You can be on time by planning the events leading up to the appointment. When you are late, it shows that you don’t respect their time, and certainly not your own time. If you respect your own time and schedule, why would you be late? Yes, many other reasons like 1)my mom made me to eat her cookies before I can leave the house 2)traffic was bad 3)my boss stopped me before I could leave and talked about nonsense which didn’t matter 4)any other ‘good’ excuse. But look, you always have a choice. You can say no to everything, of course in a nice way, and explain you have to get to an appointment so in order to be on time you will have to end the conversation but you will keep it in check.
It is those people who are early to appointments who have empathy and truly care about your well-being.