Literally anything. Options turning out to be very valuable. Getting acquired by a company you really wanted to work for. Randomly getting promoted. Meeting someone who will get you that FAANG job via a backdoor. Meeting someone you'll go on to create a successful business with. Maybe even meeting someone who will teach you to be very good at these competitions.

Point is, if one completely drops out the chance of any of that happening is basically 0. If you stay involved in one way or another, it may happen.