1. They have to be confirmed by the other branch of government, so it's not just the president picking.
1a) We have a system that is in many ways outdated, and badly needs reforms in many key areas
1b) Many places here have elected judges, so...it could be worse than having presidential/Senate appointments for the Federal courts?
2. Because, as you have seen, due to 1a), whether or not a particular octogenarian lives or dies can make a profound difference on the laws of the country
2a) Congress has been very, very feckless for a long time
2b) Also because of 1a), the courts have the final say unless their decision gets overturned by a Constitutional Amendment, which is very hard to do (again see 1a)).
2c) Also because of 1), the nominations are inherently political because those doing the appointing and confirming are themselves political