I also have a 2014 Escape, and the reason for this is actually explained in the owners manual.
The section under "Recirculated air", on. p.104, says the following:
Note: Recirculated air may turn off automatically (or be prevented from turning on) in all airflow modes except MAX A/C to reduce risk of fogging. Recirculated air may also turn on and off automatically in Panel and Panel and Floor airflow modes during hot weather in order to improve cooling efficiency.
Also on p.105 the manual says the following under "HINTS ON CONTROLLING THE INTERIOR CLIMATE":
Note: Prolonged use of recirculated air may cause the windows to fog up.
Note: To reduce humidity build-up inside your vehicle, do not drive with the system switched off or with recirculated air always switched on.
I have not had a need for the MAX A/C setting that much, where I live. With most of the other settings, recirculated air shuts down after 5 minutes. If you have a need for heat (instead of A/C), try enabling both the "Instrument Panel" (button "H" shown on manual p. 103) and "Floor" (button "I" shown on manual p. 103) mode at the same time. This seems to keep recirculation on much longer.