They may be able to confiscate my stuff, but I will at least make them put in the work to target me individually and make them find that judge and that witness and that warrant. Doing that for -everyone- is infeasible and expensive which was the exact point of the constitution. It is designed to clip the wings of hopeful authoritarian elements of our government.
Also, because I control my technology, and my encryption keys, the constitution gives me one other major protection. The right to not self-incriminate, or, the right to not give them additional rope to hang me with.
No one knows my decryption passwords but me, and no one can compel me to reveal them legally.
It is exactly because the government does not always play fair, as you point out, that every citizen owes it to themselves and each other to limit their power.
Meanwhile you give up all rights and control of your data when you agree to the terms of service of Apple or Google. They will hand over your plain text data without your knowledge or consent if you merely say the wrong trigger phrase.