So little or nothing is known about these two Apostles, except their names, and even there there's some confusion of memory. (And that should be a reminder of humility to not a few bishops nowadays!) So why do we remember them with a Feast?
Well, they were Apostles, chosen, sent, the proclaimers of the New Israel, the beginnings of the new Church. And we are members of the House of God built upon those foundation stones of the Apostles.
Further, they--the Apostles--gave us the banquet of Christ's Body & Blood, the saving waters of Baptism, the cleansing forgiveness of Penance, and the words & deeds of the Sacraments.
And their sound has gone out unto all the world, and it continues to do so in their hand-picked successors the Bishops of the world--who recently gathered in Synod to pray and talk and proclaim the Beauty of the Eucharist.
So even if Sts Simon & Jude are obscure Apostles, well, so too are most of the Bishops. Yet here we are, listening, celebrating, praying, and receiving the Sacraments that draw us closer and closer into the Beauty of Jesus Christ.