TwoSix
Everyone's literal second-favorite poster
The system is designed to give an edge to spells of a higher tier. Combined with the limited high level spell slots and limited spell preparation, this is definitely one of my favorite parts of the system. Prepping a low level scaling spell has an inherent advantage in that you have a lot more slots to cast it with. (Doesn't apply to warlocks, of course.) If you want to have multiple spells capable of doing the best damage possible for the spell slot (fireball for 3rd), you have to make the trade off of prepping a spell that can only be cast in that highest level slot.With the way D&D spells scale, should a 3rd level Burning Hands be equivalent to 3rd level Fireball, or is the system made to give an edge to spells that are inherently a higher tier?
Having damage scale purely with spell slot (by having burning hands do 8d6 at 3rd, for example), would incentivize spellcasters to prep predominantly low level spells for blasting, and use high level slots for functions that can't be duplicated by lower level spells. I'm not saying that's bad, of course, but it's much closer to the 3.5/PF paradigm of "blasting is suboptimal", and 5e made a deliberate course correction away from that.
(Side note: don't use fireball in any comparison of spell scaling damage, as it's intentionally stronger for its level to encourage fireball using wizards because it's a classic D&D trope.)