Because it did - and then it tried to claim adjusting the amount that the deliverers were being paid by an amount that exactly matched the tip amount was not wage or tip theft.
They were careful to word it as "take home pay guarantee". That guarantee looks at the actual payment per delivery, plus tips, and makes it up to a minimum.
It seems clear from all the marketing materials I've seen.
Doordash can simply argue this guarantee was on top of the regular pay, and was totally optional, and every contractor only stands to gain from this guarantee.
I'm pretty sure the whole aim of this case is to crucify doordash in the court of public opinion, despite their case being strong in an actual court of law. My elected politicians shouldn't be allowing that - if there are gaps in the law, address them directly!
The federal minimum wage is set to $7.25 per hour, with a very clear exemption for tipped workers, that the employer contribution only needs to be $2.13 per hour as long as the tips bring the total wage up over minimum on a weekly basis. If the employee gets lower tips, the employer is required to pay additional wages to bring their total wages up to the guaranteed minimum. See: https://en.wikipedia.org/wiki/Tipped_wage
The problem isn't that DoorDash is doing some new, nefarious thing. They're doing exactly the same thing a restaurant does when they pay a server somewhere between $2.13 and $7.25 per hour depending on how customers tip. The problem is that apparently most people don't understand how tipping and wages for tipped employees have worked for traditional restaurants for decades.
Because if that were allowed an employer could hire you at $20/hour (for example), and then decide at the end of your day to change your pay rate to $10/hour and that would be ok - because by your definition that isn’t wage theft.