Why is the seventh verse often sung in place of the fourth in "Amazing Grace"?

Question

In "Amazing Grace", the fourth verse:

The Lord has promised good to me
His word my hope secures
He will my shield and portion be
As long as life endures

Is often replaced with the seventh*:

When we've been there ten thousand years
Bright shining as the sun
We've no less days to sing God's praise
Then when we first begun

This baffles me, because this verse does not seem to fit the theme of the other verses, nor does it feel the same (rhyme and meter are identical, but it just sounds weird and jarring next to the other verses). The fourth verse is not particularly offensive,depressing, or otherwise upsetting (especially compared to 5 and 6, which discuss dying and the end of the world, respectively). So why is it replaced with the seventh verse?

*I say seventh because six verses were written by the original composer, and this verse was written by an unknown person and added some time later

Answer 1

This is entirely speculative, but I would guess a combination of three things:

1) The complete song is a narrative with life, death and afterlife. Omitting the middle verses makes for a jarring transition, but it does preserve the beginning and end of the structure.

2) The seventh verse strikes a more triumphant note than the more meditative intervening verses.

3) That verse probably was well suited to the tastes of the era that first appended it to the song, and persisted perhaps because the song became widely known in the 3-verse (1,2,7) format during that same time period. Choices like that become self-reinforcing over the course of time.

Perhaps like you I've always disliked the seventh verse and preferred the others. Maybe shifting tastes will restore the original version of the song.