Because you overslept. Because you weren’t looking. Because you arrived too late, too soon, unprepared, unexpected.
Or, you simply didn’t care.
But that’s okay. You will have another chance 3 seconds from now. Missed it? 12 minutes from now. Missed it? An hour. Missed that? Tomorrow. That one too? Next Wednesday. Next month. Next year…
Chance is as common as oxygen. We breathe it in all the time, take it for granted just as often.