Because both the Democratic and Republican Parties want it.
On abortion, everyone wants the ultimate "fix" to the human consequences of lawless, loveless copulation.
On illegal immigration, the Republicans want the cheap labor and the Democrats want the cheap votes.
Both parties need to be destroyed and remade from the ground up.
Give him time (and a couple million enthusiastic active supporters), and Trump may be able to accomplish quite a bit on the political front. On the spiritual front, God help us.
My older son will tell you that abortion (among other social crimes against humanity) is an inevitable result of philosophical (classical) liberalism, in both its modern permutations: progressive liberalism (Democrats), and the “conservative” flavor of liberalism (Republicans).
He will tell you that liberalism (including both permutations) is condemned by the Church.
And thus, we social conservatives don’t really fit well with what are really libertarians (the “right” side of the right-left divide of philosophical, or classical liberalism). We will always be beggers at the table of a party driven by markets, commerce, and atomistic autonomy.
The Jesuits often have a bit of an inkling of this, but their solution is to ally themselves with the progressive, Democrat side of philosophical liberalism. But the Jesuits do pay well.