First of all, thank you very much for your comment.
Bottom line? The wall simply wont work. Neither did the "Great" Wall of China!
In addition, a quote a 2017 article from The Reason sums up the current motivation quite nicely:
"President Trump's wall would be a mammoth expenditure that would have little impact on illegal immigration. But perhaps that's not the point. The campaign's goal was to plant an image in voters' minds of what making America great again would look like. The president's goal may now be to create a symbol, an illustration of a nationalism that says to the world that although people of all kinds may want to come here, America was created by and for Americans."
