There is a reason it isn't seen/used more, and that's cause it's really more a labor force participation number. Like the reason the percentage of women is higher in this metric is most likely tied to things like stay at home moms.

Things like underemployment or disenfranchised workers are good to keep track of, but there are people who do move out of the typical workforce (retirees, stay at home parents, etc.) that I wouldn't count as unemployed.