But being late isn't simply about you. Punctuality isn't merely a formality...it's an obligatory element of efficiency. When you're late to a class it's easy to tell yourself "Oh well, I'm the only one who's affected.". But what message are you sending your teacher? I can almost guarantee you that he/she is going to write you off as a person who doesn't give a shit, doesn't want to be there, and therefore isn't deserving of what they have to offer. What is your logic in self-sabotaging yourself like that?
This is why bosses have so little tolerance for lateness. The message it conveys is "I don't want to be here, I have better things to do, this place isn't worthy of my respect." Your employer is going to write you off as lacking integrity...
...and there is no forward advancement (not to mention paychecks) for people who lack integrity.
My professors don't seem to care actually. I have yet to have trouble getting letters of recommendation or permission to use them as references. If I don't appear to give a shit and my grade is high, I would think that would be a sign that the class is too easy for me. Unless the professor is egotistical, I really don't see why he'd care. If they want grad students, then the class being too easy for me is a good sign. Now, if I went to grad school and pulled that shit while teaching some class, then it would be an issue. Then again, I have had professors who were habitually late to class.
Have you been to university recently? Attendance is really only a big deal in business, liberal arts, and social sciences classes where attendance appears to matter to the professors. My math and computer science professors sure don't give a shit. They know what they're teaching is actually difficult and don't need to coerce attendance in order for most people to show up.
In regards to work, it definitely can be a problem and has been a problem. My excuse, justified or not, is diagnosed adhd. If I really cannot get my sorry ass to work on time despite a higher salary and interesting work then I'll definitely have a problem.