> I wonder how many instacart/uber orders I would need to have to offset the cost of a car, assuming I can bike to most of my needs.

Not that much. One site[1] lists the TCO of a compact car at around $33k/year if you drive it for 15k mi/year for 5 years. That works out to $550/month. Of course, if you're comparing this to getting ubers, there's no way that you'll be driving anywhere near 15k mi/year, so the TCO of a comparable car is probably $450/month. That's a lot of money to spend on uber/instacart, but keep in mind that if you have a modest commute of $20 each way, that only works out to 11 round-trips a month, or half the working days. So if your lifestyle is such that you don't need to drive to work most days, and you don't any other similar uses for cars (eg. picking up kids from school and/or driving them to extracurriculars), then by all means uber everywhere rather than owning a car.

[1] https://www.kbb.com/new-cars/total-cost-of-ownership/

I've got an ebike that takes me anywhere within ~10 miles easily, including picking up/drop off kids), and I'm a remote worker (though I could bike to the office easily.)

You're in the minority. Most people cannot use a bike for this stuff. They live too far away or the roads and/or terrain are not suitable for bikes.

I have a friend whose only reasonable option to commute to/from work is uber/lyft. He spends more each month on that than I do on my car loan. He can't afford to make a downpayment for a car loan of his own, because he is spending that money on uber/lyft. This is a vicious and familiar cycle in America.