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DoorDash now warns you that your food might get cold if you don’t tip
(www.theverge.com)
This is a most excellent place for technology news and articles.
It's part of tipping culture because it uses the acceptance of tipping to slip this bidding system in. It also doubles as a tip because there is no separate tip option and tipping is expected for delivery. I'm sure more people wouldn't mind "bidding" low if it just meant getting their food later. Instead there's also the specter threat that a disgruntled worker will tamper with their food for daring to make a low "bid".
You're more likely to not receive your food then someone tamper with your food.
Just the plausible existence of a threat is enough and tampering has certainly happened before.