Most governments spy on their friends and allies - for several reasons. Firstly, you know where your enemies stand, that's why their called enemies. Allies are a different matter, you need to know if they're going to change their policies in a manner inimical to your interests.
Secondly, information on what your allies are up to (including details of their personal lives) are very useful when it comes to negotiations with them.
Thirdly, it's easier and the consequences of discovery are generally far milder for your controllers (although their agents, if locals, may not be so lucky). It wouldn't surprise me if the vast majority of "spies" are based in "friendly" countries. As an agency chief you can then justify the numbers employed and your budget - hey, they're all busy, right?
Then of course there is all the usual spying to do, digging out commercial secrets, military technology, etc. The French and Israelis have form here - both have been caught spying in the US.
Basically, everybody does it and always have (see Venetian history, they've been credited with starting the ball rolling). The dumb thing is getting caught.