Why not? "Fourth Amendment Issues"

Here is the next installment of public opinion about TSA's naked scanners:

Commenters also addressed concerns related to the Fourth Amendment. The vast majority of these commenters stated that use of AIT constitutes a violation of Fourth Amendment rights. Individual commenters stated that AIT fails to meet the standard of a constitutionally permissible search. Specifically, some individual commenters stated that TSA could not conduct such searches without a warrant. Individual commenters also stated that neither the purchase of an airline ticket nor a desire to travel is sufficient to give TSA “probable cause” to conduct a search.  

Others stated that AIT is impermissible under Federal case law. Several individual commenters cited the holding in U.S. v. Davis, in which the U.S. Court of Appeals for the Ninth Circuit held that administrative searches must be “no more extensive nor intensive than necessary, in the light of current technology, to detect the presence of weapons or explosives, that it is confined in good faith to that purpose, and that potential passengers may avoid the search by electing not to fly.”42 Several individual commenters stated that the AIT screening process fails to meet this standard because elements of the scan and the opt-out alternative are too intrusive, and the scope of the scan is not tailored narrowly enough to exclusively identify weapons, explosives, and incendiaries (e.g., AIT is able to identify items such as adult diapers and women’s sanitary products, which commenters stated are outside the scope of threats TSA is trying to identify). Individual commenters recommended alternative search methods that they thought were less invasive and better suited to meet TSA’s need, such as x-raying suitcases, using WTMD, and only using AIT as a secondary means of screening. 

Other court cases cited in the comments to support claims that AIT violates the Fourth Amendment include: U.S. v. Pulido-Baquerizo, 800 F.2d 899 (9th Cir. 1986), U.S. v. Skipwith 482 F.2d. 1272 (5th Cir. 1973), U.S. v. Hartwell, 436 F.3d 174 (3d Cir. 2006), Camara v. Municipal Court, 387 U.S. 523 (1967), Missouri v. McNeely, 133 S.Ct. 1552 (2013), Katz v. U.S., 389 U.S. 347 (1967). An individual commenter also cited a court decision pertaining to virtual strip searches, Reynolds v. City of Anchorage, 379 F.3d 358 (6th Cir. 2004) to support opposition to AIT. 

An individual commenter observed that, even though AIT use was not found to be in violation of the Fourth Amendment in EPIC v. DHS, the subsequent issuance of an NPRM, which does not specify the degree to which AIT will be used to promote thegovernment’s interest, may result in TSA’s failure to meet the balancing test applied to Fourth Amendment rights cases.