Ha! I actually went to numerous ATMs in Santiago all of which couldn't dispense cash (Santander and BBVA were two I recall). Also the queues for the ATMs were 10 deep for the ones that did have cash (like Banco Estado). Weirdly enough some of the banks only have one ATM... while a few blocks away a bank had 6! So I guess it's all luck where you go.

I should have mentioned the closing times I described were in Vina Del Mar. All the banks I went to in that city close at 2pm. None were open past that point. I walked to 6 - all different ones (Banc of Chile, Santander, Corpabanco, Banco Estado, BCI and BBVA). It may be as you say that some in larger cities are open later. But not in Vina Del Mar.