The snmp set command is used for example to manage interface settings with CiscoView.
There are of course many more possibilities and when you are changing your network to snmp v3, it will be desirable to use it on the LMS as well to achieve higher security.
You can do this gradually (i.e. per device) if you want because v2 and v3 are able to co-exist on the same network.
Regards,
Leo