Mainly because "We The People" allow our rights and liberties to be trampled on.
"They that can give up essential liberty to purchase a little temporary safety, deserve neither liberty nor safety. They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety. Those Who Sacrifice Liberty For Security Deserve Neither."
In other words, as "We the people.." allow the government (i.e., via laws and LE) to continuously erode our freedoms (constitutional rights) under the guise of safety and/or security, we will have neither freedom nor safety.
True; It never seems to occur to them when they get a new device to ask whether they should use it however they please, they just do so until told what they are doing is illegal. And yes, we would all be better served by a better informed populace who would actually vote most of the time.
Even if the evidence is thrown out LE will still use the technology. They just won't admit it or try to get a warrant based on it. And it ll be up to you to prove that they were using it.
Well, it's good news / bad news.
This decision is clearly some of the greatest news I have heard in a long time. Now the bad news...
1. The DoJ has generally had success winning these on appeal. For instance, placing a tracking device on your car without a warrant was ruled to be legal by the supreme court. Almost certainly, this will be reversed on appeal.
2. Here's the really really bad news. Knowing that using Stingray for civilian law enforcement is on pretty shaky ground, the DoJ rendered one of their rulings a few years ago that end up having the force of law. (Like was used to protect agents who conducted waterboarding from prosecution.) DoJ has determined that the use of Stingray even for civil law enforcement is protected by national security requirements for secrecy about Stingray's full capabilities. Thus it is the stated position of DoJ that federal agents are expressly prohibited from revealing to the judge or prosecutor that data was collected using Stingray, even if ordered to do so by the judge. In other words, judges will only throw out Stingray evidence in those rare instances where they accidentally became aware that Stingray was used. In most cases, they will not know, and by "law" cannot be told, so this rulings has very little effect at the federal level