It is not just Yeshivos who have added breaks and cut instructional time.
When I went to college, semesters were 15 weeks plus exams.
My oldest had 14 weeks including exams
Many college semesters are now 12 weeks.
Cutting instructional time allows institutions to cut expenses while still raising tuition. Shutting down in winter also saves on heating costs.
If the cost of running the schools was not so high and income so low, we would not be seeing all these days off