I suspect this obvious be the counter-question why not to use it, right?
Well, I can't really tell. The sky opened up and a voice told me not to do so....
European markets are definitely different from the US and legal discussions inside the European Commission take a long time, but there is a lot going on there.
But apart from this: Only we as sellers have the knowledge where (landing-page) to best lead our customers in detail for a given keyword. In favour of the best user-experience, which google also claims to have in mind. Designing optimal landingpages deserves as much information as possible about the preceding user-action. What I am missing in the transferred information is mainly:
Which of the keywords defined in my account was responsible for this specific user and how much did i pay for it?
All this information is coded in the gclid-parameter transmitted, but to my knowledge only google knows about the algorithms to re-decode this parameter for the analytics framework.
Maybe I am wrong about this. If you have a link about how to decrypt this parameter, please post it or send me a pm.