Your professor may not bat an eye if you show up late for a class, but you can't pull that in the real world. When an editor needs something done ASAP, and you're not there because you're hungover/slept through your alarm/had a "thing," that's on you. Yes, emergencies happen, but tardiness should be an exception, and not the status quo. Besides, you should want to make the most of your time in the office—it's the only way to actually learn the ins and outs of the industry.