Government licensing is sometimes preceded by a professional society creating a certification. For GIS, considering its use and the faith many put in the info gleaned from them, a certification by a reputable body is something for which the time has come, or perhaps even overdue.
Derek,
Are you referring to the "professional certificate" itself or the GISP reference on the page? There's been a thread on Esri's GeoNet forums about whether getting a https://geonet.esri.com/thread/169450&apos ;">GISP is worth it.
The "professional certificate" is just post-graduate training. Although they're positioning it as professional development for people already working in the field, I bet a lot of students are actually trying to break into the GIS field. I know that's true of two programs near me that are post-graduate (one is a master's, the other is a certificate). I would expect any truly professional development certificate to have courses on web/online GIS and/or programming/automation of workflows.