It's not as if the latter are ingrates, but the social ritual of showing gratitude is not there among them, and maybe in some small way, that does breed less thankfulness in the long run...
I find religious people passionate about following the rituals of their religion (for many more than the intention), in a similar way as atheists are passionate about other rituals (their sport, their eating routines, etc.).
For me the absence of thankfulness equals more with awareness. Should I be thankful I have a house? I prefer to be annoyed other people don't have, or that I can't do better (ex: have a house that generates less carbon, etc.).
I was dead for what we assume to be billions of years since this universe popped up, and soon I will be for what we understand to be far, far longer. These moment are precious, and those meals and the people we share them with are too. It makes so much sense to express gratitude for them.
That little moment to remind yourself that it’s all borrowed from the universe and will need to be given back is, I think, essential to actually living. Without that appreciation, does any of it really matter at all? Without it you’re only seeking the next thing to desire. Eventually there won’t be a next thing to desire, and you’ll have never had a chance to savour any of it.
Where it goes wrong though is if we take it too far and start connecting this to some non-existent deity, which in turn makes us construct an incorrect model of the world (such as if we’re not thankful for the food, then next year there will be a drought as a punishment).
I suppose codifying beneficial practices into religion or spiritual beliefs is just part of being human.
Also, I think it depends on how you come to these rituals. If it's just something you grew up with there's a good chance it's just some words you stumble through before a meal.
It has the advantage that it is compatible with most (all?) preligions, certainly the Abrahamic ones.
Try it as a therapeutic. To release all the angst and problems before going to bed.
(If you recall your catechesis, that's laying your your problems at the feet of the cross)
> (such as if we’re not thankful for the food, then next year there will be a drought as a punishment).
It's funny that you mention this, because two thousand years ago, a new religious movement came up that believed exactly that (Christianity).
There's however also a problem with too much agency. It breeds anxiety, discontent, unhappiness. Not everything in your life is under your control, and expressing undirected gratitude is one way of acknowledging that.
The result? I definitely find it's helpful navigating the ups and downs in life. Like any other skill, if you practice gratitude you can be grateful even when you've had a significant loss, and it really helps you pull through that. Vice versa you can remain humble through significant improvements in life.
Humans have been fighting against "chance" for the whole evolution (chance of starving if you don't catch something, chance of suffering if you take a bug, etc.). I fully agree, you should not feel responsible for it, but you should not like it (or thank it) either.