Outlets without grounding can be a safety issue. Electrical shocks can result when an outlet is not properly grounded. Newer home built under modern codes are required to have grounding for all electrical outlets.
Older homes may not have grounded receptacles. Using adapters is not a good practice, due to the fact that they still need to be grounded. You can ground to the box if it is hooked to metal conduit.
This is rare in residential homes. The ground wire is a safety feature the prevents electrical shock in the event of a neutral failure.
Homeowners that have outlets without grounding may want to consider upgrading their wiring. This is a big undertaking and beyond the scope of this article. You will need to hire an electrician. It is possible that you can get grounding installed on certain key outlets, such as those that need GFCI protection. Again you will need to consult an electrician or develop basic wiring skills of your own.