This is an interesting premise, but I think some of your conclusions might benefit from a little scrutiny.
Anyone can transition without any medical or psychological intervention whatsoever. It happens all the time and it's pretty much been happening since the dawn of history. Medical and mental health interventions are only prescribed when GRS is desired, and even then there are surgeons who will offer this procedure using an informed consent approach. Not many, but they're out there.
GRS is certainly not a requirement for a successful transition, and more and more people, particularly younger trans folks, are choosing not to do it. No therapy needed or prescribed.
Saying that similar advice is not given to cisgender people undergoing comparable changes is just not true. In the first place, comparing GRS (or even non-op transition) to a job change, a move to another country or beginning college is an inadequate comparison. These things are significant events, but they are not necessarily life-changing nor are they irreversible. A better comparison would be that of a terminally ill patient who desires to end their own life under a sanctioned Death with Dignity process. Before the life-ending medications are administered there is most certainly significant psychotherapy. This is not to express that the patient is incapable of making this decision, but rather to validate that he or she is, in fact, capable of making the decision and has done so with a sound mind.
One final note - psychotherapy does accompany, in one way or another, several of the stressful life transitions you mentioned. Most universities do have mental health centers that offer students and faculty free or low-cost therapy, mental health counseling is available to inmates, national guard soldiers can scarcely go a day through the deployment and redeployment processes without being offered counseling (and this happens in country as well), and in many social work, psychology and professional counseling programs therapy for students and interns is encouraged. In some internships and agency placements it is required.