I think there are a various factors contributing to medical students not ranking family medicine as highly, and family medicine residents choosing not to practice full scope family medicine:
1) As Edict mentioned, growth of allied health professionals with increased scope and a perception that this will ultimately replace family medicine. However, I have seen teams where nurse practitioners, nurses, pharmacists, and family doctors co-exist and work well together - minor hiccups aside. For example, nurse practitioner led pap test clinics and preventative care screening, well child visits tag teamed with nurse and family doctor, etc. Which leads in part to the second point:
2) Many different practice and payment models. Most residents (myself included) will train as part of a family health team where the aforementioned team dynamic between various professions does work to support a variety of patients. However, most doctors practice in a fee for service model. The idea of trying to manage all the care that we are lucky enough to share with allied health professionals in a team based setting, alone in a more typical practice is daunting. Team based practice helps consolidate well defined roles for healthcare professionals and can help address some of the concerns around "scope creep". Moreover, patients are becoming older, the medicine is more complex, and yet compensation models have not changed in most parts of Canada, though I am hopeful with the longitudinal family physician model in British Columbia. It is crucial to implement models that actually acknowledge quality and complexity of care that family doctors provide; perhaps this includes reimbursement based on quality metrics like how caught up patients are in preventative care, how accessible their doctor is, how many ED visits for their patients, and so on.
3) With increased complexity, both in terms of medicine and the infrastructure we work in, comes increased administrative demands on a family doctor. It is on the family doctor to assess every referral (declined referrals, referral notes, redirected referrals, etc.), test result (sometimes even those which we did not order but have been advised we need to follow-up on, for example, incidental findings while a patient was admitted in hospital or findings while they were being investigated by a specialist), government forms, workplace and insurance notes, on top of the usual in terms of documenting patient encounters. Obviously, inefficiencies in electronic medical records, referral systems, health technology, etc. all compound the issue.
4) Mental health infrastructure. It is sorely lacking. Trying to get adequate supports for patients with complex mental health needs is like pulling teeth. Family doctors are essential and at times overburdened with providing psychiatric care for patients once an acute episode of mania, or suicidality, psychosis, etc. has passed. Again, when not working in a team based environment, the family doctor may end assuming role of social worker or therapist which they are not trained to do (nor in an ideal world would they have to). Psychotherapy is expensive, and not everyone has insurance/coverage. It is especially unfortunate because we often tout this as first line therapy aside from medications and yet funding programs/program planning is deficient.
5) The future move to a 3 year program. Only time will tell how this will play out in terms of implementation and what they end up choosing to do with that third year. But I cannot imagine many medical students choosing 3 years of family medicine residency over a different specialty in the current climate, at least not as a first choice specialty.
I have a lot more I could say. And this is not to add any further negative press to the field. I have come to love family medicine. It is the specialty of relationships. And all the above issues can be addressed. But our professional groups, government and leaders need to come together to advocate for us. I like to think of myself as not particularly prone to hysterics, but I do worry that without change we will slowly see this field fizzle away. I recently watched a CBC video, a day in the life type of thing, which I will leave here: