The only reason to ask my why is to subtly shift my thread topic into being about some problem and whether it's actually a problem and whether some idea you have solves the problem better etc. In other words asking why is a point blank attempt to change the thread topic.
No, the reason the 'why' is important is because one needs to know what the end goal of the change is to comment on whether or not it accomplishes that.
Now before you actually start trying to defend your asking of me "why" as some noble gesture of trying to help me out I want to point out that this comment reveals your true intentions.
Oh no, my true intentions revealed!
You already believe there couldn't be something broken with the game and that I have no legitimate reason for actually wanting the change and that this proposed change adds nothing of value to the game,
Glad you can read my mind and know what I'm thinking.
Though no, there are a lot of things in 5e that need design polish. The problem is that generally the designers of the game know how their system works better than someone doing homebrew; and their design has the benefit of extensive playtesting. That doesn't mean it's perfect, somehow the beast master ranger got through playtest, but it does mean that one should approach redesigns with caution or risk throwing the game's balance off wildly.
Removing something that is assumed in this edition, that casters have something functional to do with their turn even if they don't burn a resource, is a big change to make without having a solid design reason why. The design reason, the "why," is critical as to whether or not your solution is a good one.
Are casters too strong, and you think they need a nerf outside of their big resources? Do you feel cantrips in some way compete with martial characters and their damage output? Do you want cantrips to just feel super weak and spells to feel stronger generally? There are a lot of reasons one could dislike cantrips as they are, and each one would require a different assessment and a different approach. In order to know if a fix is appropriate, first one needs to know the problem.
You getting defensive when asked why shows you probably shouldn't be asking the general public things like this.
so your question about why is revealed as just bait so you can get a discussion started on why the change isn't needed in the first place.
Anyways, thanks for being exhibit A on why I refused to answer the "why" question in the first place.
You're welcome, I suppose. It's still a totally relevant question if you are serious about wanting a critique of the homebrew.
This sounds a lot like current 5e to me: "You either have adventuring days where your casters run out of spell slots and are forced to use totally useless cantrips, or you have adventuring days where they get plenty of rest and have more spells to throw around and never use cantrips at all."
Some groups play like that, some don't. This change would ensure that yours has no choice but to play like that. I think the most important question to ask yourself is: "Would my change be fun for the players in my group?" I don't think it would. I don't think most players would enjoy having their already piddling at-will damage functionally removed.
Given that, I'm not sure how criticizing my change with a criticism that could just as easily apply to current 5e helps support your "all 5e changes are bad position".
It might be possible you've characterized my view inaccurately in your unnecessarily defensive response.
Actually in terms of DPR helping on a fighter's attack or casting a 1d8 cantrip would come out about the same
It depends, but mostly this statement wrong. If you have a melee character who can hit reasonably hard (assuming something like sneak attack, sharpshooter, great weapon master is present), the advantage on a big hit is going to far, far outweigh a d8 of damage. At level 11 you are probably going to have a melee character who can hit harder than 1d8+5, and the increased chance to hit and/or crit on a big attack is going to dramatically outweigh throwing a d8 out.
Ignoring the question of "why" entirely, your homebrew is just a bad idea because while some groups have casters who go nova, run out of steam, and rest... your change would make that playstyle mandatory. Suggesting that it's mandatory right now, as you seemed to do earlier, is just not true.