Just because you can spy on everyone...
... doesn't mean that you should.
The problem is that the Security Services see their job as "protecting the country" and they'll protect it so much that whatever made it worth living here in the first place gets trampled underfoot in the process.
Meanwhile they're telling the government "Look, X, Y and Z happened (or could have happened) because we weren't able to read everyone's mail/ monitor everyone's phone calls/ check what website people are visiting/ see who's talking to whom etc etc" and claming that the only way they can prevent terrorist attacks is to be allowed to do anything they want and trough huge amounts of information on everyone in the hope that, by making a bigger haystack they can find some more needles and, regrettably, our governments keep falling for this.
Fortunately for us, the little people, there are a few people who actually have a conscience and believe that the right of Freedom of Expression and the right not to have the State snoop on everything people are doing is more important than preventing "terrorist atrocities" which are actually less likely to kill you than you being struck by lightning.