Arriving at every event too early, is a waste of time. If it normally takes 15 minutes to drive somewhere, some people will leave 30-45 minutes early. As another example, I meet people who arrive at the train station for 15-20 minutes before the train arrives almost every day for no good apparent reason.
My personal opinion on this is that showing up at the appointed time is optimal. Doing simple math can show that showing up early devalues your time. For this simple example, let's suppose I get paid $10 per hour to do a job. If I agree to work 1 hour per day at this rate, but I show up at work 15 minutes early every day, my hourly rate just dropped from $10/hr to $8/hr.
My agreement with my boss was to work 5 hours and receive $50 dollars, this amounts to an hourly rate of $10 per hour. What I actually DID, however, was donate an extra 1.25 hours (15 minutes per day over 5 days).
I will point out that the word "unnecessarily" is key because depending on the negative impact/cost of being late, it might be a good idea to allow for extra time. for example, showing up an extra hour early for a non-refundable flight to India might warrant spending some extra time waiting around "just in case". Leaving 15 minutes early to catch a train is probably not warranted, especially if there's another train leaving within 15 minutes of the one you're trying to be early for.