If the parking has not jetways, there's no reason why front stairs wouldn't be visible, especially on a default plane, unless you tried to configure it, and made some kind of mistake (in that case, there's the option to RESET the config to default).
Note that, if you have your Scenery Complexity not high enough, it's possible you are not seeing a jetway, which IS there (at the higher complexity levels), so GSX won't call front stairs, because that parking HAS a jetway.