The idea is to balance the spring and load energy. OE Glocks are heavily sprung, partly to help ensure they will go into battery with less than perfect ammo, or with crud in the chamber. I guess another benefit would be to help feed wider hollow-point (carry) bullets.
Too much spring tends to make the muzzle dive, so sights take longer to recover. If you case your ammo and arent worried about having to throw your gun in a mud puddle, you might see benefit from a lighter spring.
I use #14 springs in my G34s, with ammo loaded to ~132PF. That feels balanced to me, and the guns run fine. I use OE springs in carry guns.
There is some subjectivity in this. Bullet weight and powder burn rate are also considerations. Fast powders and heavy bullets give a quick recoil impulse and soft discharge, but you can run into mechanical problems if the gun is not supported well.
As others have said, overly light springs can allow the slide to beat up on the frame.
OE Glocks are designed around reliability in a broad variety of potential circumstances. If you can eliminate some of those circumstances, then no need to suffer performance loss trying to compensate for them.