The events included within the Commonwealth Games are far more limited than with the Olympics:
http://www.bbc.co.uk/sport/commonwealth-games/2014/schedule
I suspect that part of the reason that events like rowing aren't included is that (in theory at least)
any Commonwealth country should be able to host the Games. Hosting rowing might prove difficult for a country with no rivers!
Equally, the Olympic Games include skiing, bobsleigh, curling, etc. (They might take place at a different time to the summer Olympics but they're still part of the Olympic Games). Hosting those sports within the Commonwealth games could prove to be a bit tricky if the venue was in an equatorial country! ;-)