Why is capital loss used not showing in 2019?

Not showing where?  On your 1040 or the carryover from 2018 or to 2020?

FYI.....The 2019 column shows the carryover to 2020 not your current loss for 2019. The 2018 Column shows the carryover to 2019.

2019 Capital Gains and Losses on Schedule D go directly to 1040 line 6. And Schedule D doesn't actually show the carryover amount. To find your Capital Loss Carryover amount you need to look at your return schedule D page 2. Line 16 will be your total loss and line 21 should be a max loss of 3,000. The difference between line 16 and 21 is the carryover loss for next year.