Why do you want to watch me through the window. You can come and look if you want as long as you're not doing it to perv over me I couldn't really care less.
To keep the analogy don't we need to add two provisos though: you can't tell anyone about it or you lose your job and face prosecution (unless you can convince the CPS that there's a case against me, then you have your say in court); and you'll need to convince a judge that you have a legal need, that also serves the public interest, to observe me.
>Our email conversations with our friends and family, our video chats etc should be private. (They're not of course, they're all intercepted and stored forever, but they should be private). //
AIUI the UK Investigatory Powers Act is storing domains visited for a limited time and requires a warrant to enable access, access then only being granted to officers of a particular standing (so they can't pass the details around and the named officer is responsible if the info is leaked). Am I getting the wrong message? I've not had time to read the Act yet.
Security services are almost certainly able to access that data, but then that's been true for a long time and is covered by far more generic laws, the IPA isn't addressing that (is it?).
tl;dr - if I don't care if you sit and watch me watching Masterchef, or playing on Steam, or if you read my emails to customers, or see what I buy (just like you can if I go to a shop), then ... is there anything left that you can say to convince me I should be hiding what I do online. "I don't hide what I do IRL, why hide online"?