The more Spanish you look, the better looking, professional, educated, smart, wealthy, etc Mexicans assume you are.
A very racist culture.
I remember when my ex tried to talk to our “el Indio” gardener (once every other weekend to mow the lawn and trim the hedges) in Spanish, he looked at her strangely and said “I don't speak Spanish”. He spoke English and his native Amindian language. Had no interest in learning Spanish and didn't much care for Mexico or Mexican culture.
Can't say as how I blame him.
Throughout Mexico's history, or at least since about 1700, one faction or another has traditionally gotten fed up and seized power by force of arms, oppressing either the general populace or the wealthy landowners respectively, and just generally plundering the country about every 60-70 years.
Then whichever group was on the outside would revolt, slaughter a bunch of regime supporters, and the whole crazy cycle would start over with a new crew of Kleptocrats, but pretty much always rotating between populist, Mestizo uprisings, and Hidalgos “recapturing the throne”.
Since the last great Mexican Revolution (~1910-1922), an essentially open border with the United States has pretty much served as the “safety valve” for the hardcore, corrupt, and utterly inept Socialist Elite Hidalgo cabal that seized power in the wake of the populist revolt's power vacuum, and which in spite of some back and forth political jockeying, has held on since the twenties.
They know they can plunder the country, and every time conditions get too bad at home, their disaffected Mestizo population just heads North. Mexico City encourages it because it furthers their leftist political goals as well.
They used to go home when things improved a bit. Now, mostly because of the drugs, it never does, and since there's so much more money (legal and illegal) for them here, they just come and stay.
In some ways, I can sort of understand that. If my choices were living under a Socialist/Narco dictatorship, letting my family starve (or worse), getting killed by drug runners, becoming a drug runner, or heading to Canada, I might pack a bag and start walking North too - although I'd probably stay and fight the drug runners, `cause I'm stubborn that way.
Ed Abby said it best when he suggested we meet every one of them at the border with a rifle and a box of bullets, and tell them to go home and fix their own problems. Then we can talk about being good neighbors.