Scotland is too much of a risk for Labour to invest the time and effort to win back those votes. The SNP's dominance has cost votes for Labour, but it is too difficult to tell when and whether their popularity will fade.
Labour's growing disconnect with English voters is of greater concern. Considering the vast majority of parliamentary seats are within England, Labour would be far better suited investing in those voters. Scotland's politics have become its own, and the time may have already passed for Labour to maintain its power in the country.
Labour has some soul searching to do in the aftermath of the 2019 election, but they won't find it in Scotland.