Google Play Services
Take you're Android phone, find "Google Play Services", this is a service that is REQUIRED by Google's contract with handset makers to be running on your device.
This app lets Google install software onto your device without you knowing. It runs all the time, and cannot be stopped, if you try to remove it, it will remove every app on your phone. Yet if you can root the phone and kill it, then it's not used to run the apps.
It accesses everything from Wifi, network, location, audio, video, SMSs, messaging, apps, contacts. Nearby devices even. It can do EVERYTHING it wants under Google remote control. Which in turns means every snoop around the world has that access and that control.
Take a look around you, how many android devices are withing earshot of you? Those potentially are listening. How many camera phones are watching you now?
So you are a journalist, a politician, perhaps you've expressed a view that a spook disagrees with, or work at a company that is targeted for industrial spying. Well your phone could be tasked with spying on you.
Do you believe big multinationals should pay their taxes? You might think its radicals or extremists that are spied on (and that you're safe because you're not radical or extreme), but this was one of the issues that the UK "Forward Intelligence Unit" spied on in 2010. Daring to demand companies pay their taxes got you put under police surveillance. Yet surely that's the consensus? That companies pay their taxes?
Without any checks on surveillance, and with nobody to answer to, the police can target you for their surveillance fishing without you ever knowing or having the right of challenge. Your private discussions recorded, your location tracked, your phone calls monitored. There's zero accountability and zero penalty for misuse.
Search on "COINTELPRO", this was the US version of political surveillance, with FBI targetting people expressing political views at odds with the Presidents. Read the Church Committee report. That was then, now things are MUCH WORSE. Look at where Theresa May's lot are now, far far far beyond the nightmare scenario of the Church Report.