Why the Ents went extinct - love is us, not you and I.

Ent:
When Spring unfolds the beechen leaf, and sap is in the 
bough; 
When light is on the wild-wood stream, and wind is on 
the brow; 
When stride is long, and breath is deep, and keen the 
mountain-air, 
Come back to me! Come back to me, and say my land is 
fair! 

Entwife:
When Spring is come to garth and field, and corn is in 
the blade; 
When blossom like a shining snow is on the orchard 
laid; 
When shower and Sun upon the Earth with fragrance fill 
the air, 
I'll linger here, and will not come, because my land is 
fair. 

Ent:
When Summer lies upon the world, and in a noon of gold 
Beneath the roof of sleeping leaves the dreams of trees 
unfold; 
When woodland halls are green and cool, and wind is in 
the West, 
Come back to me! Come back to me, and say my land is 
best!

Entwife: 
When Summer warms the hanging fruit and burns the berry 
When Straw is gold, and ear is white, and harvest 
comest to town; 
When honey spills, and apple swells, though wind be in 
the West, 
I'll linger here beneath the Sun, because my land is 
best! 

Ent:
When Winter comes, the winter wild that hill and wood 
shall slay; 
When trees shall fall and starless night devour the 
sunless day; 
When wind is in the deadly East, then in the bitter 
rain 
I'll look for thee, and call to thee; I'll come to thee 
again!

Entwife:
When Winter comes, and singing ends; when darkness 
falls at last; 
When broken is the barren bough, and light and labour 
past; 
I'll look for thee, and wait for thee, until we meet 
again: 
Together we will take the road beneath the bitter rain! 

Both: 
Together we will take the road that leads into the 
West, 
And far away will find a land where both our hearts may 
rest.

JRR Tolkien, The Two Towers

They, like many of us, did not make it to the last three stanzas.