You are not being selfish but expressing a legitimate need.
I grew up with a mother who never told me about sex, menstration, dating, or anything female. The only thing she told me once (don't know what prompted it) was that my dad could have sex every day if it were up to him and she had this could care less about it look on her face. So I think this is a common attitude among some women.
The problem with posts like yours is that your wife is not the one asking if sex is important and what to do if her husband tells her he feels rejection and is suffering.
If your wife was posting, I would respond as follows:
You (the wife) sees sex as another chore to do. Someone else demanding a piece of time from you. Your husband, however, probably sees sex as an expression of his love and desire for you.
When you say no to sex, you cause your husband to experience shame and rejection for expressing an emotional and physical need. Saying no to sex is one of the ways you tell your husband through actions that you no longer care and value him as your lover.
If you were always being rejected, would you feel good about yourself as a woman. Picture this: you put on your sexiest lingerie and your husband turns around and says "not now there's a game on." Replay this scenario multiple times and ask yourself how would you as his wife feel? Unwanted, unloved, less of a woman.
The above is what I would ask the wife to get her to sympathize with you, the husband.
I would also get very frank with the wife and tell her:
You say you are not on the mood and have a low sex drive. Bluntness here, well if you can manage to get a tampon in you can certainly handle a penis. Get some flavored lube and lube up.
You are sleepy, well grab an expresso then lube up.
You are hurting, well go to the doctor. If you are suffering vaginal pain, then get flavored lube and engage in oral with your husband.
No matter what perceived expectation that you feel your husband is not living up to (ex. not doing enough with kids or chores) never withhold sex as a punishment.
You, as the wife, vowed to love your husband and right now he is feeling hurt and rejected. As the wife, you hold the remedy for this. Engage him and initiate. Having sex on a regular basis actually makes you prone to want it more.
Sex is physically healthy for both of you and bonds a couple together. Have sex because you want your marriage to thrive.
A wife can initiate and experiement with her husband to find out what she likes. As a wola