Matthew, Mark and Luke are the three Synoptic Gospels ('seen together'). They cover a lot of shared material in similar groupings and order.
Unlike the gospel of John, they have a significant amount of overlap with one another. A literary relationship can explain this.
Luke mentions that in putting his gospel together he was aware that others had undertaken a similar exercise AND that despite this, Luke still wanted to create his gospel. It met a different need than these other ones.
Luke 1:1
Since many have undertaken to set down an orderly account of the events that have been fulfilled among us, 2 just as they were handed on to us by those who from the beginning were eyewitnesses and servants of the word, 3 I too decided, after investigating everything carefully from the very first, to write an orderly account for you, most excellent Theophilus, 4 so that you may know the truth concerning the things about which you have been instructed.