Its different areas in the baggage bays sometimes a completely different part of the building. Also you have to get someone to move them which is always at a cost.
And I don't really understand why they don't just circle the pax. Some airports do, and others just open a door and move them through while checking boarding passes. And others they make them go back through security, some times getting rescreen other time just through a side gate.
There have been various reasons given to me.
Airport security policy.
pax tax.
Bus availability.
Immigration rules.
Customs rules.
But more than likely it comes down to handling fee's