Bearing in mind I'm not at all the target audience for this sort of thing (wrong country, for starters)!
Usually when starting at a new clinic or if it's been a little while since anyone's asked, they will ask whether I'm thinking about getting pregnant in the foreseeable future, because, they go on to tell me, diabetic pregnancy requires serious planning beforehand and serious work during, so it's not something to be undertaken on a whim and without letting the clinic know my intentions! Usually it's just a very casual sentence or two thrown in, just part of a sensible medical discussion and not really obtrusive.
I think that's sufficient really, and probably what the guidelines are getting at - I don't think anyone needs or wants their doctor to go into full detail about preconception and pregnancy unless it's already on the table! On the other hand, diabetic women of childbearing age need to know that they DO need to put these things on the table to begin with, and depending on the patient education and general standard of care they've gotten, they may or may not realize that. BUT it's important that the message be given out early and often that 1) it is possible to carry a pregnancy as a diabetic and 2) though it is possible, it's still a Big Deal and best not to just "let it happen naturally". That last, I think, especially for T2s, given that they and their diabetes are so often given very little consideration, or for teens and young women who might not be thinking as many steps ahead as they need to be - who might not realize they need to think any steps ahead at all!
At every appointment though seems a bit much. Once a year, maybe, but eventually you've heard it enough times you don't need to be told again. Seems like the guidelines may have more to do with doctors (GPs especially) forgetting that they need to do this bit from time to time, rather than with what is actually convenient or useful for the patient.