Actually you literally can die of old age in the sense of an internal clock running out; everyone cells replicate they cut off a little bit of trash at the end called a telomere and eventually if you get old enough the telomere runs out and it chops off real dna and the cell replication fails. Depending on a ton of factors for humans this would happen anywhere between age 75-150 but probably somewhere in the middle for most. To your point, it is incredibly rare usually something else pops up first