Wikipedia article says that this is an interesting side effect of it and that it is even used for “chemical castration”. Although it also mentions a number 8% in relation to libido suppression, but they might only mean it for the women who are the usual intended recipients of Depo-Provera.
Anyway, so could a more targeted treatment be developed to somewhat reduce the male libido, optimized for maximum safety and reversibility as opposed to for whatever goals that Depo-Provera was optimized for? Perhaps if something like that were done it could be used by single soldiers on deployment or be given to teenage schoolkids who need to focus more on their studies?
Incidentally, if this type of testosterone reduction therapy were given to teenagers, would it interfere with the normal growth?