They appoint Supreme Court Justices. Those appointments decide our constitutional rights for decades or centuries. For that reason alone, it's worth all the fuss.
I'm going to respectfully disagree. I disagree about the gravity, but I don't feel I can make that argument satisfactorily with the time I have now. But even aside from that, the relationship between my vote for a presidential candidate and the eventual appointee is very indirect--in my case, the presidents I have voted for have always chosen vastly worse Justices than the candidates I voted against. I think you'd have to somehow agree fervently with one of the major party's ideals, but also take the broadest reading, in order to really be satisfied with their appointments. I personally think there's a lot of value in combining a progressive legislature with a conservative judicial branch.
I want to respectfully disagree, but I'm afraid there's no truly respectful way to call your statement what it is: naïve and dangerous.
Based on the current composition of the Supreme Court, replacing a single judge could have dramatic, fairly immediate, and nearly irreversible real-world consequences to the citizens of this country. Whether you agree with those consequences or not, you'd be hard-pressed to argue that the stakes aren't high.
This is probably why talking politics is frowned upon here. I appreciate your perspective, and I especially appreciate your civility, but I don't think we can go further in this venue.
In a perverse way, maybe the only good thing George W. Bush did as President was to show people how important it is to not elect a really bad candidate for President.