Practically speaking... Math is one of the most essential skills necessary for "life as we know it." From handling money to basic home repairs, you can't function well without a basic foundation in math.
Developmentally speaking... Math studies train the mind in the most basic ideas of logic, cause and effect, order and the concept of truth.
On a more spiritual level... Studying Math can be an excellent opportunity to practice the virtues of patience, neatness, perseverance and obedience (for children AND their parents!). Making sense of the order of the world around us through the logic of Mathematics helps us in understanding, even to a small degree, our Creator as well.
What about "Catholic Math"? Some people interpret the words of Pope Pius XI, in his encyclical On Christian Education that "every subject should be permeated with Christian piety" as "every subject should be permeated with religion." They take this to mean that we need Catholic Math books in which word problems are about religious subjects in order to more fully fulfil this description of what a Catholic education should be.
Dr. Mary Kay Clark, in her book Catholic Homeschooling argues for the benefits of Math books with Catholic word problems as a response to those publishing Math texts with secular and/or anti-Christian content in the word problems. I think she sees it as a way of promoting Catholic culture in a day when Catholic culture is rather hard to find.
Although I agree that we need to promote a genuine Catholic culture as much as we can, I think we need to look at the idea of why we as Catholics study Math. We don't study Math in order to learn Religion and I think that some parents are missing that point.
I would go so far as to say that religious-themed word problems don't make a Math program more Catholic because that simply isn't the point. I think that a Math course that is truly Catholic would start with an understanding that there is truth and lead children clearly through the elements of what they need; wisely presenting the material in accordance with how children learn.
Children should be taught to pursue their studies for the greater glory of God. Discussions could touch upon order and design.
Our faith encompasses everything in our lives; not just those things which are explicitly religious. Religious word problems in Math texts certainly aren't bad in and of themselves, but I think it important that parents and teachers aren't confused into thinking that religious content fulfills our obligation as Catholics to teach our children Math.
What Math materials are problematic to our faith?
On a more superficial level, there are individuals and organizations attempting to promote their agenda (such as "normalizing" the homosexual lifestyle) through content of Math word problems. Clearly agenda-driven materials aren't worth bothering with. Besides, the Math probably won't be very good either.
A perhaps more substantial (to the field of Math), but subtle problem lies in books which attempt to destroy the truth, order, beauty and virtue we're looking for by denying that there is a right answer... (oops I lost the last page)