You can tell that the balance of game states both with respect to historical game states and potential future game states (i.e. how a game has, will, or could unfold) is important to single-player and cooperative experiences with a simple application of reduction to the absurd: If you modify solitaire such that you can name yourself the winner every time you lay down a card, you have made the game far less interesting to most people, and insofar as we're talking about quality as a function of appeal, worse for it.
You are dismissing the fact that there are 2 ways to consider balance here. The first is balance in terms of a character against the environment and the second is in respect to 1 character in comparison to another. I am very much interested in having a game where the environment is balanced against the player, the challenge is after all, part of what makes the game interesting. However, I have very little interest in whether 1 class is balanced against the other. Your absurd case thus does not sufficiently fulfill the criteria here, because, as I pointed out above, you can very well make the game itself challenging to a player who is using these mechanics, simply by making the game itself take advantage of them as well.
Then you can look at it from a content perspective, as greater balance tends to have a multiplicative effect on the amount of content a game effectively offers without conditions that are detrimental to most players. For example, if Rogue and Wizard were to be grossly overpowered, you would be introducing a selection bias for all other classes, which would look something like "I will choose [Barbarian/Warlock/Bard/etc.] if and only if I am looking for a greater challenge," or "I will choose [Barbarian/Warlock/Bard/etc.] if and only if my feelings about their creative appeal outweighs my interest in clearing the game efficiently." Whereas if all the classes are balanced, those selection biases wouldn't exist, effectively offering a greater number of options to a greater number of players.
These biases can have their place, say when implementing difficulty settings for example, but generally speaking they must be implemented with great intention, and it will very, very frequently produce shoddy design if they sneak their way into a game by accident.
The 5e rules are incredibly basic and there is not much to keep track of, which is great, if you are playing a tabletop game and don't want to be boggled down by small details and the game is driven more on roleplaying than on combat, but when you have a computer keeping track of all of that, it makes for a really barebones experience. There is not much room for creativity in combat and your options are exceptionally limited. Adding mechanics like surfaces does help to remedy that situation and adds depth back to the game. And yes, the rules, if implemented 1:1 as per the rulebook, are simple enough so that most encounters are "solved" for me on the very first round of combat. I can lay out exactly how the fight will go and what I need to do to win. That makes for a very boring game, from my perspective.
Then you can look at it from a content perspective, as greater balance tends to have a multiplicative effect on the amount of content a game effectively offers without conditions that are detrimental to most players. For example, if Rogue and Wizard were to be grossly overpowered, you would be introducing a selection bias for all other classes, which would look something like "I will choose [Barbarian/Warlock/Bard/etc.] if and only if I am looking for a greater challenge," or "I will choose [Barbarian/Warlock/Bard/etc.] if and only if my feelings about their creative appeal outweighs my interest in clearing the game efficiently." Whereas if all the classes are balanced, those selection biases wouldn't exist, effectively offering a greater number of options to a greater number of players.
These biases can have their place, say when implementing difficulty settings for example, but generally speaking they must be implemented with great intention, and it will very, very frequently produce shoddy design if they sneak their way into a game by accident.
This over here was what I talked about when I mentioned the idea of being, "jealous of your neighbor." The fact of the matter is, the game is probably going to be balanced around a party of 4, where the party has a rogue, cleric, wizard and fighter. Whether or not surfaces are included is not really going to change that, because the casters there would have access to surfaces as well and even if surfaces do not exist, you can already skew the balance by taking different party compositions. Being, "jealous of your neighbor" is imo not a good enough reason to make a game less interesting.
