It's a bandaid fix for the bad inventory system, that only introduces more UI inconveniences. Thankfully you atleast not forced to use it.
Install the Black Desert Launcher if the game doesn't start.
The launcher will appear if it's installed.
If it doesn't, try to run your downloaded launcher.
1 Run BlackDesert_Installer_NAEU.exe to install the Black Desert launcher.
2 Start the game once installation is complete.
It's a bandaid fix for the bad inventory system, that only introduces more UI inconveniences. Thankfully you atleast not forced to use it.