In many locations, it's not within the airlines control. Some stations don't have the bandwidth to support a full airline system implementation. In others, the equipment is not common use, so the application can't be installed. It only supports the local airport's software.

Finally, in some stations, the preference is simply not to put it in, due to the seasonal nature and frequency of flights. It is better to let the local staff use what they know, then ask them to learn a new system they might use once a week. In thrse scenarios, using the airline system will at best delay the plane and at worst corrupt your booking.