Stop whining, and work to get the best you can. Or if you really see it as so pointless, just slack off and get a worse grade. In reality, there is no great amount of difference between a 2:1 and a 2:2, and people can do worse in final exams for all kinds of reasons, not just because they're not good enough.
An attitude where "why should I work for it because X scenario may occur" is what won't get you a job. How will you explain yourself in a potential interview if they ask about your commitment to the field. "meh couldn't be arsed putting in extra to get a 2:1 since I know FOR SURE it wouldn't help get me that job which hasn't been advertised yet". With high competition, you really have to show you care, and appreciate nothing in life is a walk in the park.
But sure, you throw common sense out the window now, and see how that fares you in the real world of rent, food, bills, council tax, loan repayments etc.