Please see Bereishis 49:4,5 Why is Reuven addressed in the 2nd person and Shimon and Leivi in the 3rd person?
This is a good question. A possible answer might be, according to what the Tzror Hamor says. Being that Yackov wanted to give rebuke to some of the shefotim, in order that they should accept his rebuke, he first told them, “and listen to Yisroel your father”- meaning that these words are being said out of love. Then he said, “Reuvain you are my beloved son, however because of…”. It could be that therefore the torah uses this terminology for the first of those who got rebuked as an example for Shimon and Levi to learn from that all of those rebuked were told so out of love..