The more complete tradition is to celebrate Great Vespers on Saturday evenings and the eves of feasts, Matins the following morning, followed by the Divine Liturgy. The Divine Liturgy is only celebrated in the evening on certain days, when it is always preceded by Vespers.
Beginning in the 1960's, some Greek Catholic and Orthodox churches began celebrating the Divine Liturgy in the evening, to accommodate workers, families that had to travel significant distances to church for feastdays, and situations where a priest served several parishes. In the late 1970's, the liturgical commission of the Eparchy of Passaic came up with a proposed order for preceding this Divine Liturgy with Vespers, as is done on those days when the Divine Liturgy is supposed to be held in the evening.
By the 1980's, the Eparchy of Parma had a formal outline of this service, suggesting that if a Divine Liturgy WAS going to be celebrated in the evening, it would be better to follow the "more traditional" pattern beginning with Vespers; this would also serve to familiarize the people with Vespers in the hope of eventually restoring the more complete cycle of services.
For myself, I would certainly rather see regular Vespers served in the evening - but not if it would mean that a parish never had the Eucharist at all.