Random encounter doesn't mean deadly encounter.
It only mean that you have to be carefull a bit more and think a bit more before burning all your spellslots and "features slots"..
These sentences are somewhat contradictory. If a random encounter isn't deadly, then you don't need to save resources for it (besides to finish the encounter more quickly I suppose). It's just tedious and time wasting - which I don't necessarily disagree with as a disincentive to long rest, but this is now an entirely different motivation for these random encounters than "strategic use of resources."
If random encounters are implemented, they'd need to be deadly in order to encourage any kind of resource management. And if anything, they'd encourage more long resting. Players who typically long rest often would still long rest often because they'd worry about dying to the random encounter (or they'd more likely just set Random Encounters to "Off"). And players who don't long rest often would rest sooner to prevent a possible TPK to random encounter.
Designing a dungeon to require a full long rest's worth of resources, putting dedicated camping sites within the dungeon, and/or requiring that you spend limited rations to rest seem to me like a better way of encouraging resource management.
