Why is it that Mexico doesn't have customs stops like Canada?

Question

For Mexico, you could drive straight into the country without the hassle of waiting for the guards to check your passports. Canada does have customs stops at the border with USA.

Why is that?

Answer 1

Some cars/individuals are stopped and checked, some are not.  It is the same at the border and at the many military checkpoints.  You never know if you may be the one that is stopped and checked.