It's probably fairly common.

For the United States, a good source of data on undergraduate math programs is the American Mathematical Society's Statistical Abstract of Undergraduate Programs in the Mathematical Sciences in the United States. In their most recent report, dated 2015, you can find in Table SP.18 (page 67) some data on curricular requirements in four-year math degree programs. You can see there, for instance, that among PhD-granting universities, 26% didn't require any computer science courses for any of their mathematics majors. A further 19% required it for some of their majors but not all. There are separate figures for masters-granting universities and undergraduate colleges which are not dramatically different.

The numbers may have changed in the past five years, but I suspect not by a lot; changes in curriculum requirements usually involve a lot of bureaucracy and happen slowly.

So I suppose that the people who set curriculum at those institutions simply don't share your opinion of the importance of programming coursework, or feel that students can make their own decisions whether to take it as an elective.

(Whether or not those institutions are acting wisely is certainly a reasonable topic for debate, but this site is not the place for debates.)

It's probably fairly common.

For the United States, a good source of data on undergraduate math programs is the American Mathematical Society's Statistical Abstract of Undergraduate Programs in the Mathematical Sciences in the United States. In their most recent report, dated 2015, you can find in Table SP.18 (page 67) some data on curricular requirements in four-year math degree programs. You can see there, for instance, that among PhD-granting universities, 26% didn't require any computer science courses for any of their undegraduate mathematics majors. A further 19% required it for some of their majors but not all. There are separate figures for masters-granting universities and undergraduate colleges which are not dramatically different.

The numbers may have changed in the past five years, but I suspect not by a lot; changes in curriculum requirements usually involve a lot of bureaucracy and happen slowly.

So I suppose that the people who set curriculum at those institutions simply don't share your opinion of the importance of programming coursework, or feel that students can make their own decisions whether to take it as an elective.

(Whether or not those institutions are acting wisely is certainly a reasonable topic for debate, but this site is not the place for debates.)