B/X Known World
We do know what they were thinking. They explicitly said so in the DMG. People just quibble about it or haven’t bothered to read the DMG.Which is why I included it. We don't know exactly what they were thinking, but they have stated that when they were designing 5E that it took into consideration a lot of history and old school gaming style. That they wanted to pattern it on how older games were played. Those older games? A lot of them focused on dungeon crawls.
If I could wave a magic wand we'd have more options and guidelines for alternative rest rules to fit your campaign style. We don't have that so I use gritty rest rules and a house rule extending the duration of some spells.