I don’t know a single man who has been competitive at the national collegiate or pro level (i.e. a contender for winning NCAA outdoors, indoors, or XC) in the 5k-10k who doesn’t regularly do 15+ mile long runs. I’m sure some exist (mainly mid-distance runners who move up), but 70-80 minutes is about the average length of a regular easy run of the top guys I follow on strava (5k PRs ranging from 13:20-13:45), and they’ll usually cover 10-13 miles in this timeframe (70-80 minutes), and then they run 16-20 miles on the weekends on average.