Staying sufficiently hydrated is crucial to recovery following a long run. Acting like those who don’t take water during a long run are pu$$ies is ridiculous. Maybe they’re just wiser than you.
The amount needed depends on the temperature and the person, but assuming a long run of 18-20 miles that takes between 1:50-2:10 depending on pace and distance, I have found that the overall muscular wear and tear the run puts on my legs decreases significantly if I take sufficient water. For cooler weather (sub 50deg), this might be one water stop of taking in only 8oz or so at about 1:20 in. For warmer temps of 70+deg, I’ve taken two to three stops and had up to 32oz of fluid. The warmer it is the more valuable I’ve found taking gatorade instead of water to be.
Staying sufficiently hydrated is key to preventing your muscles from breaking down more than they should. I’ve found it’s often the difference between being able to come back and effectively handle a Tuesday session (following a sunday long run) and being in a bag so to speak.
As a side note, JK speaks quite emphatically about the importance of taking water during a long run in his writings.