Jeb? believes that protecting America from illegal invasion is not Conservative. And, a wall would not help the supply of cheap labor to his political supporters.
The easiest way to stop the inflow if illegal aliens and increase the voluntary outflow is to stop the enticement. Stop anchor babies and any use of government benefits. More importantly, require stringent E-Verify rules and enforce them. Most importantly, severely punish those who hire illegal aliens without the stringent E-Verify rules. Thereafter, you can streamline deportation rules. However, self deportation is the easiest and cheapest way to achieve success. The problem is that JEB? and his country club supporters want to increase the inflow of cheap labor, not hinder it.