The waiting list to "get here legally" is so long as to literally cause entire generations of applicants to have to choose between adhering to the term of their documentation-period, of staying "illegally" and waiting for a hearing date to come up. The backlog for those seeking US citizenship from Mexico is right around 20 years...and most of the BIA/DHS removal proceedings that I've been involved with involve individuals who have applied for some form of legal status and have had the term run while waiting on the process to actually...well, work. There is a lack of funding, a lack of manpower, and a lack of a clear mission as to what the US immigration policy is--and what policy goals ought to be achieved with regard to the enforcement of the laws that are in place.
Something to chew on, especially for those in the "they should follow the rules and come here legally!" camp.
to see the rest of my "oversized" signature. "Leadership is diving after loose balls." -Larry Bird