In his book, From Last to First, Charlie Spedding, who was third in LA and 6th in Seoul, cursed the fact that the IAAF or IOC only allowed water stations every 5K in the heat of Seoul in 1988.
As to DNFs, as someone who would never get close to a qualifier on his best day, those who make it can do whatever they want. They've earned the right. And I agree, although I'm not at his level, with the sentiment from "I was a dropout", "Most guys at my level aren't going to sacrifice future performances or risk injury to finish if things aren't going right." I DNFed in the heat of 1984 NYCM and never regretted the decision.