Vying for Control by Creating/Completing Rhyming Couplets

This is something I've noticed before, in Richard II.   Here, in 1 Henry VI 4.5, it is a contest of wills between Talbot and his son.

Talbot's first speech (ll. 1-11) is entirely unrhymed.  It ends as follows:

Therefore, dear boy, mount on my swiftest horse,
And I'll direct thee how thou shalt escape
By sudden flight.  Come, dally not, begone. 

John's six-line response (ll. 12-17) plays off this with a rhyming line, and ends with a completed rhyming couplet (giving his father no opening to complete a rhyme):

Is my name Talbot, and I am your son,
And shall I fly? O, if you love my mother,
Dishonor not her honorable name
To make a bastard and a slave of me!
The world will say he is not Talbot's blood
That basely fled when noble Talbot stood.

The next four lines (ll. 18-21) are a back-and-forth where each of Talbot's lines is countered in rhyme by his son:

TALBOT: Fly to revenge my death if I be slain.
JOHN: He that flies so will ne'er return again.
TALBOT: If we both stay, we both are sure to die.
JOHN: Then let me stay, and, Father, do you fly.  

And indeed John's rejoinder in l. 21 is the start of a 13-line speech with six rhyming couplets ll. 22-33.  Thus, John again ends with a rhyming couplet that gives his father no purchase to complete a rhyme ("Here on my knee I beg mortality, / Rather than life preserved with infamy.").

The next ten lines (ll. 34-43) are once again a back-and-forth where John counters each of his father's lines in rhyme:

TALBOT: Shall all thy mother's hopes lie in one tomb?
JOHN: Ay, rather than I'll shame my mother's womb.
TALBOT: Upon my blessing I command thee go.
JOHN: To fight I will, but not to fly the foe.
TALBOT: Part of thy father may be saved in thee.
JOHN: No part of him but will be shame in me.
TALBOT: Thou never hadst renown, nor canst not lose it.
JOHN: Yes, your renownèd name. Shall flight abuse it?
TALBOT: Thy father's charge shall clear thee from that stain.
JOHN: You cannot witness for me, being slain. 

But at this point John's own unrhymed couplet (ll. 43-44) finally gives an opening for his father to complete the rhyme (ll. 45-46) -- the one and only instance in this scene.  Indeed, Talbot immediately wastes his chance for verbal one-upmanship, yet again leaving an opening for his willful son to complete the rhyme (l. 47):

JOHN:
You cannot witness for me, being slain.
If death be so apparent, then both fly.
TALBOT:
And leave my followers here to fight and die?
My age was never tainted with such shame.
JOHN:
And shall my youth be guilty of such blame?

John's last speech in this scene (ll. 47-51) is rhymed, ending with a rhyming couplet (foreclosing any further verbal jiujitsu).  His father's last speech -- likewise in rhyming couplets -- thus bows to the inevitable as he realizes he cannot persuade or overmaster his son (ll. 52-55):

There here I take my leave of thee, fair son,
Born to eclipse thy life this afternoon.
Come, side by side together live and die,
And soul with soul from France to heaven fly.

Exeunt.