This has nothing to do with the rules. This has to do with the DM (and/or the adventure creator) and with the players.
It does have to do with rules. Not 100%, but it does have something to do with rules. It's true that there's no way to use rules exclusively to prevent the 15-minute workday. But you can make it less of an easy choice.
First, everyone has to realize that the 15-minute workday doesn't exclusively mean 15-minutes. It could be 2 hours or 4 hours. It's whenever the group feels like they need to stop at an artificial point. This pretty much means any time it's not night and the party feels the need to rest.
Here are the contributing factors in each edition:
3e:
-A EL X or EL X+1(and sometimes EL X+2) encounter does not challenge an APL X party. They can defeat it without using any resources that would be considered significant by extremely tactical players with somewhat optimized characters(which means using any spells in the top third of spell levels available to them or hitpoint damage that would require healing spells in the top 3rd of the spell levels available). Often these battles can be defeated with the non-casters just attacking until the enemies die and using Wands of Cure Light to heal everyone to full. If this is the power level of the encounters you use, a party can often fight nearly infinite of these encounters a day before stopping to rest. This is directly a rules related issue. It has to do with the math interaction between the defenses of the enemy, the attack bonuses of the PCs, the damage dealt by the PCs and vice versa. If a particular CR 8 monster can be taken down by a APL 8 party in the first round with melee weapons before it has a chance to act, it is most certainly a rules issue.
-A higher level encounter(EL=APL+3 or higher) almost always poses a significant threat to the group. Dire enough to use up significant resources. Higher levels spells are very limited in number. If you are level 5 and have 2 3rd level spells and you need to use them both to defeat one of these encounters, you most certainly won't survive a second encounter of that difficulty. But unless you go to at least APL+4, you rarely actually threaten TPKing a fairly optimized party. Most APL+3 encounters are easily defeatable if you use your higher level spells each round of the combat.
-There is no limit on the number of times you can rest each day other than the 8 hours it takes to do so. Nothing stops a party from starting at 7 am, adventuring until 8 am, then sleeping until 4 pm, adventuring until 5 pm, then sleeping until 1 am and adventuring again for an hour. Even if you have a roleplaying deadline(for instance, when the sun comes up tomorrow the ritual will be complete), you can still get a couple of rests in the same day(in fact, I had a group who would cast 12+ hour long duration buffs, sleep for 8 hours and refill all of the slots used to cast them).
-No rules based drawback to resting.
4e:
-Most encounters of level=APL or APL+1 don't seriously threaten the party, but they do use up healing surges. Which means that there is a distinct limit on the number of encounters, even easy ones that you can do in a day.
-Most encounters of level=APL+2 or APL+3 seriously threaten the party, but can be defeated without using dailies. They are slightly easier with dailies, but they aren't required. They don't just threaten to spent the parties resources, they threaten to actually beat them. Smart play can defeat these encounters. But not without healing surge loss. And it always poses the risk that a bunch of bad die rolls will still cause the party to lose.
-Encounters of level=APL+4 or higher are extremely difficult. Generally smart play AND dailies are required to survive. Lucky die rolls can sometimes pull you through, even if you don't have dailies.
-Extended Rests are limited to once every 24 hours by the rules.
-Milestones and Milestone activated magic items encourage continuing rather than resting.
What this means is that in 3e you generally have one of two situations:
-The enemy doesn't use up your resources at all(or very little), in which case the PCs don't feel challenged and they have no reason to rest at all
-The enemy is hard enough that you don't want to fight a second encounter of this difficulty without resting, which encourages the party to rest every chance they get.
In 4e, you get 2 situations as well:
-The encounter was a little easy but significant in a long day of easy encounters(after 5-10 encounters of this difficulty, the number of healing surges lost will add up until the party decides to rest)
-The encounter was approximately the right challenge(with some being slightly easier or harder) and feels like it could legitimately defeat the party. There is probably a limit of 2 or 3 of these you'd want to throw at a group in the same day before they'll run out of dailies and decided it's better to rest than continue on.
Obviously, in both editions there is incentive to rest and incentive to keep going. But the overwhelming mechanical incentive in 3e is to rest after every encounter. Or at least after every 2 or 3.
