We make an effort to make sure that our newer members attend Church activities as often as possible. Being a member of the Church is more than just attending meetings on the Sabbath - the gospel and the Kingdom of God on Earth (the Church) becomes part of our daily lives. For new members, attending social activities outside of Sunday services/classes is an important part of integrating into Church culture and feeling part of the Ward/Stake family.
In a slightly different way, the same concepts apply to our non-member investigator friends. When they come to activities (like Ward parties, for example) they meet more Ward members (including Ward leaders) and can develop relationships with people they have already met.
In addition, they may be able to overcome any previous misconceptions that they've had about what Church members are like. When investigators only have contact with the missionaries outside of Church and then only see Church members when they're dressed up for Sunday meetings, they may wonder - Do members of our Church always dress up? Are women are expected to wear dresses all the time? Activities are a great way to show that we do wear jeans and we're generally pretty fun people!
Ward missionaries, Ward leaders, and other Ward members can encourage investigators to attend activities by #1- making sure they know about upcoming activities (when, where, etc) #2 offering a ride (if appropriate) #3- offering follow-up reminders (fliers or verbal reminders) in classes or personal phone calls.