This is strange to me. Without the game itself there's no value to the art to me. The reason I play games is to become invested in the outcome and therefore have a better experience.
Furthermore, if all you want is the art, why cheat or walkthrough? It would take less time to rip the CG, like you said?
Edit: Dear god, I just wrote wall of text! Anyways, you were looking for insight as to why walkthroughs are more important for some people, I'm trying to share some insight as to that 'other' point of view you were asking for. Feel free to skip over the wall of text as you see fit.
It's that very need to 'invest' time in a game that is the problem. If we were dealing with completed works, it's one thing, but (using DMD as an example) some games have been in development for a couple of years now, and have not reached completion (and may never reach completion).
While I still use the preview pics at the top of a given thread or whatever to make an initial judgement as to whether I might possibly be interested in a game, they don't tell the whole story. But the main problem is that, due to the WIP issue, people want to know if there's sex in the game or not at this time, and with whom. If if the 'sexy fun time' isn't with the character(s) that are piquing their interest, then they simply aren't interested. Game descriptions are usually all about what the developer says he wants in the story eventually, not what is actually in the game at a given point in time.
Again, it's a time thing. After playing dozens upon dozens of porn games, in various stages of (in)completion, you become more interested in just what you may be investing your time in before committing to it. And really, most of these are just visual novels with a few decision gates thrown in. Sure, that's essentially the same as a comic, and some 'games' should just be done as visual novels.
So Walkthroughs can answer a LOT of questions, even if you don't follow them religiously. Example: This cute girl I like in the art, do I get to bone her in this version? If not, it's a waste of my time as the other characters don't interest me.
Sure, if you find the game in a place like here (where there are forums) you can try to scan the forum thread for the game to see if it holds your answers, but decent walkthroughs generally have a lot of those answers. Also, some people's responses/opinions may not give you the answers you are looking for...
There are thousands of porn games out there at this point, so trying to figure out which one YOU'd really want to play next isn't all that straightforward. Especially since most are WIPs.
And the art style also matters. Some art just doesn't do it for people... but that's not a walkthrough issue (that's more of a CG extraction thing).
Because of the sheer number of games that are now out there, I'm also over the whole 'gallery unlocking' thing. That's where extracting the CG saves some time (so you don't have to play through a dozen times to see everything), or cheat codes to unlock the other scenes where those might be implemented (for games that let you replay the scene, thinking of the galleries in The Artifact here), but that's not an option for some games/game engines, unless someone is able/willing to unlock those for you (thinking Unity as an example). At least with RenPy games, I can do that myself with unren.bat.
Just keep in mind that not everyone is here for the gameplay, although the story may or may not interest them, depending on how much 'grind' and associated silliness may be involved to unlock that story.
Different people have different expectations and wants when it comes to adult games, just like anything else. What you are looking for isn't what others may be looking for... and also the amount of time you may be willing to invest in a game may not be the same as others...
In short, Walkthroughs can often answer some of the questions you may have before you invest your time, i.e. 'how involved is this game', 'how much content is there right now', 'how much sex is there right now, and with whom', 'exactly how do the mechanics work in practice/how much grinding/dialogue choices am I going to need to click through', etc.. And you can find a number of these answers fairly quickly in a decently written walkthrough.
Again, after the first few dozen games, your willingness to invest time in any given adult novel/game, yeah you know what you want from the game, and walkthroughs may have the answer.
Plus, as I stated before, for very intricate games (read - a number of conditions that need to happen before something happens, and if you miss one...), you pretty much need a walkthrough for those anyways. Not all games are straightforward, or well written.
Ask yourself, what was it that piqued your interest in a given game? For me, it's generally because one or more of the characters look sexy to me. At that point, then the questions entering my mind are 'is there any point investing my time in yet another storyline/game universe, or is this thing gonna be a train wreck' and 'how much work is going to be involved to follow the plotline that interests me?'
I still play games, and walkthroughs aren't always the first thing I look for, but for games I'm 'on the fence on', well things like walkthroughs and CG art can give me a lot more information about whether I actually want to invest time in that game.
Plus, it annoys the hell out of me if I have to play the same game say a half dozen or more times to unlock each 'path'. I gave up on unlocking everything in 'Play With Us' because of this. I don't mind a couple of playthroughs occasionally (if the game is good enough to warrant it), but usually I'm 'one and done, with exceptions'... due to that 'next game' always appearing on the horizon...
Again (beating the dead horse), walkthroughs will often hold a number of the answers I seek when I'm pondering maybe trying yet another game...
