If their IT department hasn't expanded their skills beyond making and maintaining those original websites, I could totally see a long delay happening before/if they join the fediverse.

More likely they aren't given the budget they have requested.

They are also probably busy doing regular IT things like maintaining the IT infrastructure.

Local news stations don't really exist in my country so I don't know how many employees they usually have but it's possible they don't even have an IT department.