It’s true that some of them still go around holding themselves out as priests, but the Church at least has an official record that the person was expelled from the ranks, which would tend to remove their responsibility for whatever the laicized priest might do. Also, in the case of the younger priests below retirement age, it relieves the Church from having to assign the priest or find some place to put him, and he is off the Diocese’s dime for his salary, benefits, health insurance etc. Interestingly, a laicized priest can still do anointings and hear confession of those in danger of death, according to this website from Diocese of Phoenix.
And just like you said, this guy Fushek mentioned on the Diocese of Phoenix website, who was a co-founder of Life Teen and was laicized after a bunch of complaints of him sexually abusing minors, is still running around calling himself Fr. Fushek and operating this rather prominent and busy “Praise and Worship Center”, which the Diocese has ordered Catholics not to attend.
I would presume that for McCarrick, the Church really doesn’t want someone of his extremely high profile getting a little condo somewhere and being out on the street, which is what seems to have happened with most of these laicized abuser priests who weren’t serving a prison term, so I’m not sure how they would legally handle keeping him out of the public eye after he is laicized. I would think if he’s removed from the priesthood, the Church no longer has control over him and he could just go do whatever.
Excommunication is a little different because it’s done in the hope that the person will reform his ways and come back to the Church, which does happen. Laicization for punishment is more like the person is such an embarrassment/ failure as a priest that the Church wants to cut ties.