The ONLY purpose of LEGAL immigration is to increase the labor supply and reduce wages of Americans. The only purpose.
No, there are many other reasons for legal immigration, some of them good, some of them bad. What matters is that the people be allowed to collectively decide the level of immigration that they would like, and not have their will subverted by politicians who are pursuing their own agenda. Increasing the labor supply doesn’t automatically reduce wages. It depends on the economic environment.