For France, the root cause for the lack of specialist in some zones is actually not that they aren't paid enough (a generalist, for instance, seem to have it's lower bracket above the median income for a family, and an average that is at 3-5 times it. Sadly, jobs such as nurse have bad pays though...), but more a part of the french medicine school: the "numerus closus". At the end of the first year, students take an exam week, and only the N first students are allowed to pass, with N being a preselected constant for that year. Not everyone is allowed to try again too. This has been criticized for some time and if I remember well was recently removed, but the cynic part of me tell me that they would have no issues crafting an exam specially to have roughly N students pass...