You're right about the "other professions being less stressful and more rewarding" than medicine. That's because unlike other profession, medicine is both a profession and a vocation. While I can't speak to the motivation of all those who opt for the stressful and sometimes less rewarding medical profession, historically those who chose to study medicine have had a "sense of calling or a strong desire" to help sick and vulnerable people. That's why many still undertake some may see as a thankless profession where after 5 years of highly demanding curricular, 2 years of foundation and an average of £60,000 of student loans debt (UK Jr Doctors) or over £200k in debt for international fee paying UK educated junior doctors, they still remain to help patients for while making less than Cosco regular employees with or without a failed GCSE.
In spite of their sacrifices, they're frustrated by the lack of enough vacancies for Specialties to enable them to become Specialists or Consultants in order to make enough money to pay off their debts.