There are a fair number of things that many people are probably OK with giving some general parameters and approving a purchase and have someone else take care of all the logistical details.

The bigger issue is that I'm not really willing to pay someone what it costs to e.g. take my car in for state inspection, run my errands, etc. I do have some services for things like getting my lawn cut but it's harder/more expensive to get someone to handle unscheduled one-off things.

Then you're perhaps not the target market.

People with that kind of money, if they're dissatisfied, they just roll the dice again.

Is that market large enough in America to hit a critical mass?

Like most personal services, it's probably a niche. In a luxury, NYC apartment? Sure. As you note they exist. But most people see grocery delivery as a luxury. In fact, I suspect even lawn mowing and maid services are used by a relatively small proportion of the population. Much less having someone take your car to the shop or the various other myriad errands that are always piling up on my todo board.