Don't know for sure but I can offer some speculation I've seen from elsewhere in the world.
Yes, airport terminals need fire escapes just like any other public building so some stairways from the boarding lounges to the apron serve in that role. They may or may not be used for routine passage of employees between terminal and apron.
The gate in this picture looks like it has two unused jetways. Possibly on the drawing board they were intended for regular use but when you lay the building down on the airport, it would indeed restrict that taxiway nearest us. Without that bit of apron being usable for east-west taxiing, there would be great difficulty passing an eastbound and westbound aircraft anywhere on the south side of the terminal complex without using runway 9R
-27L. I would surmise that the space is more useful therefore as an equipment park.
Another possibility is just plain bad planning, a malady known to strike airport managment from time to time.
When Reno Nevada built their much-needed new terminal they poured a footer for one of those huge floodlight towers directly beneath a door intended to serve as a jetway. Had the light been installed it would have passed right up through the jetway.
One problem we face here in the US is too much money. Airport authorities in many cases are simply awash in money from "user charges." (while the ailrines serving them are in bankruptcy) One airport manager I know does not answer to city, county or state government, he is sovereign, and answers to the Feds only in the area of air operations. He pays himself more than the governor of his state plus the governors of the four surrounding states earn combined. They are forever starting new construction projects, needed or not, because they have to dispose of money. Not all of their projects are compatible with the others and we occasionally end up with doors leading nowhere as in your picture.
Ironic isn't it that if passenger traffic mandated that they begin using that gate they would have to restrict air traffic to do so?
Happiness is not seeing another trite Ste. Maarten photo all week long.