is that a flavor reason or a balance reason? I can see good arguments for both, but also against both.
I knew a woman who DMed since an older edition that HATED cantrips being at will and used to do everything she could to house rule around it.
I'm not
@Ath-kethin but we moved away from 5e, due to, among other things, the ease of magic, which included Cantrips as a major issue.
The ability to always have substantial magic on hand, unlimited use, particularly when those are damaging cantrips (scaling), light related effects, etc. which help to overcome environmental conditions, made the game less fun for us. When cantrips were first implemented way back, they were small, non-offensive spells that new casters would learn and they were things like cleaning a spot, or minor mending. Now they're every round scaling Firebolts and Tolling the Dead, which do more than many first level spells in comparison.
So, for us, trying to limit or remove Cantrips was balance and flavor.
We moved to OSE Advenced and B/X as a result of the arc that continues to trend upward in terms of game power, and the proliferation of magic. While the game is fantasy, and inherently magical, our table concept of magic is more "rare and powerful" rather than "commonplace, always available to everyone, and powerful".