Long rests are important, but there needs to be a reason for a mechanical NO. I instituted a "medium rest" which was the same as a long rest, but it was done in an area the DM determined hazardous. You got back about half your normal benefits, but could make a Con save (based on how hazardous) to recover about 3/4 your normal benefits. It was a very interesting idea, but the mechanics made things a bit wonky.
My group already finds safe(er) places to rest when possible. Even spells that ensure an uninterrupted rest often allow outsiders to be aware of the group, allowing them to wait for the spell to expire. In addition, intelligent creatures will usually react to the presence and actions of the PCs, so taking a long rest allows them time to regroup and install greater defenses. In a low level adventure, my party was trying to wipe out a band of kobolds that were in the dungeon of a ruined fort. Each time they came back from a long rest, the entrance would have a new trap and better defenses, warning the players that short excursions were not a good idea. If they tried to rest in the dungeon, they'd almost certainly be found by the kobolds who would attack with overwhelming numbers. This kept them pushing on until their resources were completely expended, or they came across a group to dangerous to face.
My group already finds safe(er) places to rest when possible. Even spells that ensure an uninterrupted rest often allow outsiders to be aware of the group, allowing them to wait for the spell to expire. In addition, intelligent creatures will usually react to the presence and actions of the PCs, so taking a long rest allows them time to regroup and install greater defenses. In a low level adventure, my party was trying to wipe out a band of kobolds that were in the dungeon of a ruined fort. Each time they came back from a long rest, the entrance would have a new trap and better defenses, warning the players that short excursions were not a good idea. If they tried to rest in the dungeon, they'd almost certainly be found by the kobolds who would attack with overwhelming numbers. This kept them pushing on until their resources were completely expended, or they came across a group to dangerous to face.