Panorama looks at The Real Reasons to Upgrade Your ERP System . I think the reasons they list are pretty valid. My experience has been that a GP upgrade isn’t nearly as much work as an SAP upgrade but the points are still valid.
The Real Reasons to Upgrade Your ERP System | 360° ERP Blog
Install, Upgrade & AdminMicrosoft & the GP Ecosystem
Archived post from 2012. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.