Heres an exerpt from my featureless guide that may give you an idea why people choose to use the grip wrap instead of a magazine lock.
First lets define Featureless Builds and Magazine Locked Builds in plain English:
A Magazine Locked semiautomatic centerfire rifle has a non detachable magazine limited to 10 rounds and is allowed to have features.
A Featureless semiautomatic centerfire rifle has a detachable magazine with no round limit* and is not allowed to have any features.
Features are Pistol grip, Thumbhole / Folding / Telescoping Stock, Flash Suppressor, Forward Pistol Grip, Grenade / Flare Launcher.
* Note: while there is no limitation of the number of rounds a Featureless rifle can legally hold California still has a separate magazine limit law that applies.