It happens sometimes, I get it. You hit unusual traffic, there was a family emergency, something really time sensitive came up - I am not unsympathetic by any means, and I totally understand when things like this happen.
However, if you hit this traffic every day or you're consistently late by the same amount of time, every time: leave earlier.
If you say you're going to be somewhere at a certain time, stick to it. Don't give me an unreasonable estimate - I'd rather you tell me a later time than you consistently be much later than you say you will.
You have one of these everywhere. On your phone you're constantly checking, on your wrist, on your cable box. Look at it often and if it's looking like you're going to be late, let me know. If you tell me to be ready by 8:00, I will be ready by 7:55 just in case so if it's 7:30 and you haven't even showered yet, just tell me so I can stay in my sweatpants too. There's nothing worse than being all dressed up and waiting by the window for someone to come get you. I don't care if you will be late if you tell me, I do care if you consistently lie and say you're on your way when you're not and make me be constantly on my toes that you'll be there any second.
I had a friend who lived maybe 15 minutes from me, yet every time she left to come pick me up it would take her 45 minutes. She would say "leaving now!" when really she was just sitting down to leisurely put on some makeup. It was infuriating. The whole point of telling someone you're leaving is specifically so they know when to be ready; lying defeats the whole purpose.
Even more than being annoying though, it's disrespectful. You want me to be sitting there waiting for you, not doing other things I would rather be doing, while you take your time? By being late, you're telling people that your time is more important than theirs and not only is that incredibly narcissistic, it's rude as hell.
So many of my friends and even coworkers are like this and I don't know how to deal with it. Why can't we just agree on a time and stick to it? Why can't other people get it together enough to figure out what damn time it is and be ready when they say they will?
Late people - why???? I'm genuinely curious, I've never gotten a good answer. If you're half an hour late to everything, how come you can't figure out how to just leave half an hour earlier?