Makes no sense

Can someone explain to me why the President gets to pick the SCOTUS? I thought the whole point of the three branches was checks and balances? Doesn't seem very checks-and-balancesy if one branch of the government gets to pick who's in one of the other branches. I don't have a better alternative, since clearly the voters are even bigger dinglefucks than the President, but still... seems like a massive design flaw.