The usual argument is quantity versus quality – with most men going for the former and most women focusing on the latter. However, this is just two of the three legs on which sex rests.
The third leg is variety. Some will argue quality and variety are the same thing, but they’re not. If I feed you the same gourmet meal every day for a year, you would have exceptional quality of food, but absolutely no variety. On the other hand, I could provide you with variety but not quality by feeding you a different poorly cooked meal every day. Few of us find either of those options appealing, suggesting there is some middle ground better than either.
In some ways, quality and variety are antagonistic to each other. Learning to do something well takes practice, so the more we do a certain sex act (less variety) the better it gets (more quality).
The other part of this, at least for most women, is the energy necessary for each new sex act. Because sex is often difficult for women, any change can be emotionally challenging. There is the fear of looking silly, or not doing it well. There is the very real concern it will not provide her with orgasm, and possibly frustrate her enough she won’t be able to climax in another way. Of course, there are women who are all about trying new things; if your wife is such a woman, then go for it. Just be aware “something new” is a problem for many women – as proven by how many men complain about the lack of variety.
On a practical level, how much frequency are you willing to sacrifice for more variety? We can agree it should not work like that, but for many it does. Are you willing to give up some quantity for more variety? Would you be willing to exchange some variety for having sex more often? You probably want more of both – how has asking for that been working out? If more of one means less of the other, then you need to decide which is more important to you and focus on that one.