Non-secure encryption keys and many other paranoid reasons. Allow a crack in the wall and it will most certainly expand. You might be interested in this: http://www.theregister.co.uk/2015/11/12/snowden_guide_to_practical_privacy/
iMac (19,1, 3.1 GHz i5, 12.7.4, 40 Gb RAM); MacBook Air (1.8 Ghz, 8 Gb RAM, 10.14.6, 256 Gb SSD) Vodafone router and Devolo Wi-Fi Extender, Canon TS8351 printer/scanner.
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