This is done because they do not want us to know just how many millions of them are really here.
Their so-called estimate of 11 million is drastically downplayed from an actual number of over some 40 million.
All one has to do is do a little traveling in the US to realize this.
Southern California and the state of Nevada are prime examples of the actual numbers of illegals in the US. Most of Los Angeles area, Las Vegas, and Reno have so many that these cities remind anyone more of Mexico City or cities in some Central American country.
Here alone, there are more than triple the Federal government's estimate of 11 million, and this doesn't include the millions in other states such as Texas and Illinois.
What is more concerning than illegal immigration, if that is possible is the massive influx of Muslims into the country since Obama was in office. During the entire time Obama was in office, he admitted around a million Muslims into the US.