Mexico uses passport control almost purely as a jobs program. At the land borders only the largest cities seem to check (like Tijuana), most of them don't even glance at you. The guy at the x-ray machine has been asleep a few times.
For first world entry they just depend on the fact the 1st world country is harsher on security than them so they don't bother. Might be different if you enter from Mexico's south land border.
Trip to Mexico. Get into the hotel. We bought a few things that had the kind of packaging that is impossible to open. I said "I'll go to the front desk and ask for scissors". Without missing a beat, my daughter pulls out a full size Fiskars pair of scissors from her carry-on luggage and hands them to me. The scissors made it past LAX security theater x-ray machines, etc. Hilarious and terrifying at the same time. Mexican security caught them on the way back, so we had to donate them to Mexico's GDP.
People get worked-up about interactions at airports without fully understanding their context and realities. Just chill, don't argue, don't be an idiot and enjoy the trip.