Purpose of torque converter unlocking during decel?

[Stalker L-67]

4L80E
In 4th/overdrive I find it annoying that the torque converter keeps unlocking when taking foot of the gas pedal. Keep in mind this is factory stock trans/tune and I am creating a list of changes when I visit the tuner on the 19th.

The question is: What is the purpose/logic behind the unlocking upon throttle lift?

[2xLS1]

I would guess so vehicle maintains momentum and doesn't experience engine breaking every time you lift for better fuel mileage. A smoother feel. Remember these are factory tuned for the general public and what they expect to feel in a vehicle ride