The Holy Spirit was given to the 70 elders so they can help Moses with all the burdens of the people in Israel. Carrying the burdens of other people can be very overwhelming, this is why we need to be in good relationship with God so He can help us face the burdens of others such as family, friend, coworkers and even Gods people.
When the Holy Spirit came upon them they were able to prophesied for a short time. God know whom He want to prophesied to His people continually. Having that relationship with God is so important during these days and time.