I think it's because the order was useless in the first place. It was unneeded. Obama only issued it to ingratiate himself to his favorite, and loudest, fringe group. I don't think Trump cares that much about the issue, one way or the other.
There is supposed to an executive order that makes it impossible for the federal government to in any way penalize anyone in regards to their beliefs. In other words, the re-ordered ex. order won't remove the rights of those who, for religious beliefs, refuse to serve in any way that violates their conscience.
God bless.