DT has USB, so it could handle USB drives. It’s a matter of choice for Elektron. They chose not too. Deluge chose to add SD Card, it even streams audio. Akai chose SD card for MPC ONE. The Octotrack has a CompacFlash card since day one. Makes it soo much more flexible. Storage is cheap and fast nowadays. I just bought a 256GB SDCard that handles 170MB/s for 130EUR.
Needing a Transfer app to transfer samples feels soo outdated.