These isotopes have limited (and sometimes quite short) lifetimes. Bringing them closer to the patients means that they can be produced in smaller quantities on an as needed basis, and reduces the necessary infrastructure to transport them.
Is it correct that this is the kind of stuff used for PET scans? I didn't read the article, but my radiology friend told me that they create semi-custom isotopes for PET scans.
PET (for oncology at least) typically uses 18-FDG, a glucose analog. Unfortunately has a short half life requiring facilities to be close to the source.