A user logs into a new Sage CRM 7.3 install and can not see the option to switch to the classic dashboard.
This is "By Design".
The classic Dashboards have been deprecated in Sage CRM 7.3. A system upgraded from Sage CRM 7.2 would still have them but for a new install they would be unavailable to reference.
This will effect mobile themes in CRM if they have a dashbaord set up to display as the mobile themes use the classic dashboard.