Because that's literally one of the most common "nope, we're nixing that 100%, that won't happen to us at all ever" spell problems. It can happen literally from level 1 (goodberry, create or destroy water, and purify food and drink are all 1st-level spells obviating the "can you find food/water" angle), and becomes fully, unequivocally operational at level 5 (create food and water and Leomund's tiny hut, the latter of which is a ritual so it doesn't even cost a spell slot.) With but one Cleric and one Bard or Wizard, you can--by spending no more than two spell slots--completely eliminate an entire swathe of concerns. And not just for the party! You get enough food and water from create food and water to feed fifteen people or five steeds (so, presumably, you could choose to feed, say, six people and three steeds), and while the food only lasts 24 hours, the water is permanent.