I feel like two things kept Dallas and Texas in general from having significant LCN members in it.

One reason was the indigenous O.C. element in Texas like the Dixie Mob, Benny Binion, the Chagras, Jerry Ray James, Bandidos, etc. They are all dangerous and wouldn't like a bunch of out of state Italians stepping on their drug and gambling rackets. They had the lay of the land, knew the players, and had everything sewn up.

The second was law enforcement down there. Either it was too strict or too corrupt (probably both). They also weren't letting their home team and the money they got from them get overtaken.