You can only say you are visually and mentally disgusted with the table so many times before it isn't worth the breath
She does it because she knows she can get away with it. I'm speaking from experience.
I grew up as a complete fucking slob. I think its one of those funny things that might alternate generations. My mom kept an immaculate household and of course I was brought up to clean up after my own shit, but by the time I shipped off to college they'd generally given up on haranguing me about it. At that age it was easy for me to be like 'hur hur I like it cluttered its just who I am'.
By our third shared apartment, once we started accumulating actual possessions, the boy was fed up with me. I was home all day and it was a pigsty. I knew every night he came home and was pissy and refused to say why, its because I was on my ass and hadn't cared about the fact that everything looked like a bomb had gone off. I knew why, but I'd ask anyway. The sulleness, the 'nothing's, that was permission to continue a bad habit.
I know I keep harping on your wife's domestic failures but its because I sort've feel like I know what she's experiencing. I have no idea about the specific effect of essentially being alone all day with nothing but your children, but ennui is just that. Lack of motivation, most likely being caused by depression. She doesn't care that she lives in a mess because she is a mess. She went from busting her ass for 60 hours a week to becoming a mother by occupation. I'm not going to bother trying to opine on the specificities of whatever existential crisis she's going through, but the state of your house is a manifest symptom of it. She's aware that it is a bad thing. She knows its not acceptable, but after a certain point you are accepting the deficiency and giving her a pass for it. Because you love her. Because you don't want to fight, or whatever. Because you have fought about it before and after a while it didn't seem to do anything because she regressed right back into the same habits. Not gonna tell you what to do but if you do love your wife, there is some serious and hard-ass talks you have to have with her. She's not going to spontaneously 'get better'.