My church seems to do this a lot too, and it annoys me a lot. Some examples:
All the Way My Savior Leads Me(Probably done because Adventists are mortalist and don't believe people go directly to heaven or hell when they die.)
Christ the Lord is Risen Today (Second verse)
An entire verse of "Jesus Loves Me" was changed:
OriginalUpdatedThis was probably, at least in part, for the same reason as the "All the Way" one.
Rock of Ages (Last verse)
(See above)
A classic example in the vein of the "Amazing Grace" one (one that my pastor fully acknowledged):
At the CrossEven Christmas carols aren't immune. "Good Christian Men Rejoice" became "Good Christians Now Rejoice" (probably to make it more "gender neutral"), and nearly all the traditional verses of "Silent Night" (except for the first) were changed into something completely foreign.
One of things that annoys me the most, though, is when they set the hymns to music that isn't used for them in any other church. "I Sing the Mighty Power of God" is set to a tune that I've never heard in any other denomination, as is "I Gave My Life for Thee," "My Lord and I," and "Hark the Voice of Jesus Crying," among others. (In fact, the latter got its title changed as well, to "Hark the Voice of Jesus Calling.") I'm assuming that most of these "new" tunes were written by Adventist composers (There are a few that I know were.)Honestly, I think the mortalist updates are unnecessary too, because even if people don't go to heaven or hell
immediately after death, they do at some point after death.
I could go on and on, but simply put, hymns are poetry, and poetry is fine art. Some of these hymns were beautiful the way they were. Why change them? If you disagree with the theology, then don't sing them (or those verses, if they're not in the first one.)