Because it makes it easier for them to act violently and violate people's legal and Constitutional Rights as the linked article by Adam Serwer explains.
This line stands out: "The crime rate of CBP agents and offices was higher PER CAPITA than the crime rate of undocumented immigrants in the United States" - as shown by data on CBP's own website.
If there were law-enforcement agencies particularly ill-suited to anonymity, it would be Customs and Border Protection and the Border Patrol. From 2005 to 2024, nearly 5,000 CBP and Border Patrol officers were arrested, according to the journalist Garrett Graff, who testified about his findings to an accountability commission set up by the governor of Illinois. Information on the multitude of corruption-related charges faced by agents can be found on the CBP’s own website. “The crime rate of CBP agents and offices was higher PER CAPITA than the crime rate of undocumented immigrants in the United States,” Graff writes.” Statistically speaking, “worst of the worst” seems to describe CBP and the Border Patrol as law-enforcement agencies better than it does the people they’re rounding up.CE does not have the same history of criminal behavior, but it does share a long record of abusing its powers and mistreating people in its custody. Put succinctly, these agencies deal with people the American system has frequently treated as barely human. Now these agents have been unleashed on Americans. Putting masks on people in agencies with internal cultures like these was always a recipe for catastrophe. The Trump administration took the most corrupt, poorly trained, and impulsive law-enforcement agencies in the country, gave them masks, and turned them against American cities.
Using ICE/CBP is a manifestation of Trump's contempt for people and disregard for the health well being of Americans. Murders like Good's and Pretti's are a predictable consequence of this contempt and recklessness.