Each and every time, should a poem rhyme?

A poem doesn’t have to rhyme, they say,
It can weave words together, convey
Thoughts, feelings and stories of beauty,
That sort things out, but it has no duty
To give similar ending to line or verse,
Or a sing-songed cadence try to nurse.

Yet a poem can’t be so wild and free,
Or any great text a poem would be.
The Gettysburg Address would certainly do
Formed so clearly, with efficiency too,
But Old Abe surely not a poem was writing,
When brave men dead, ended their fighting.

They say rhyming words are a compromise,
And rarely are right for the thought we prize,
But saying it right with rhymed words sings,
And texture, character, and rhythm brings.
So negate rhymed verse ‘til hell’s been froze
But know what’s left’s not a poem—it’s prose.