They are not. CPB is busy as hell here, between all 9 border crossings.
Staffing the wall would take a bare minimum of 6000 people, given one person per mile and 3 shifts, but policy dictates working pairs, so 12,000 people. Plus all the infrastructure, vehicles, fuel, supervisors, and HR requirements.
There are not 12,000 CPB people "babysitting". Not sure where you guys get that bullshit.
And that is just having two people per mile, which isn't realistic in Arizona or New Mexico (call it about 8 people per mile), though it might be in Texas, I don't know.