It's an attempt on intimidation, because supposedly for the person travelling it's a lose-lose:

• provide all your data, and allow the US government (and any connected entities (big tech)) to use it to track and sell that data
• don't provide all your data, and when the US government suspects that you did that, they can bar entry for little reason, and/or have legal grounds(/excuse) for go after you

All around it's a humiliation and intimidation exercise