In the case of GM, and probably for the others, a series of accidents in the 60s in which entire boards of directors all died together led to a stockholder DEMAND that no more than two members of the board can ever be on the same airplane, or in the same vehicle of any kind.
While I can't say for sure that the other US auto makers have the same rule, similar retrictions applied at Boeing where Mulally, CEO of Ford, worked previously.
Where such rules are enforced (for good reasons) there is little alternative to providing individual transportation when the big guys are required to travel. I see no "profligate waste" in the modes of travel used by these guys, for this meeting.
For a meeting of the kind, it is unlikely that any of these CEOs travelled alone, and a usual contingent would include perhaps a half dozen board members and/or senior staff. Which of you would want to be the booking agent to get a half dozen people on separate commercial flights to assure that they all get there on time and can return to get back to business on schedule?
While the airplane cited for the GM CEO is a fairly nice little puddle-jumper, a $35M jet is far from a "luxury aircraft" in my experience. It's about the minimum you can get with turbo engines and minimal IFR instruments, of any kind. While I'd guess that the plane used by the GM CEO has nice seats and pleasant upholstery, it's still a plane that a person of normal height has to crouch in to walk to the potty.
Executive jets (and autos) commonly have communications equipment rivaling what's in Air Force One, and secure contact with headquarters is another DEMAND from the stockholders that additionally requires "special arrangements" for travel.
As to building autos that the people want, GM sold more vehicles than any other maker worldwide last year, despite a rather poor market. And they're not the biggest employer, ranking FIFTH in number of employees among auto makers. (There are some outside the US, in case you haven't noticed.)
GM offers more than a dozen (I think it was 16 or 18 for the current model year) models with EPA fuel economy ratings of 30 mpg or better. While there are some autos with higher ratings commonly used elsewhere, the "most efficient" ones common in Europe are mostly diesels that DO NOT MEET US EMISSIONS LIMITS and cannot be legally imported (or built) here due to regulations demanded by Congress and applied by the Administration.
The auto makers are in trouble now because CHANGES MADE BY THE REPUBLICAN CONGRESS AND IMPLEMENTED BY THE CURRENT ADMINISTRATION have destroyed the banking industry, and lines of business credit previously available to them have been shut down. The LOANS that they are requesting quite likely will be repaid in timely fasion, and are no more than (probably less than) the lines of credit they would have used in the course of normal business had not the ADMINISTRATION AND REPUBLICAN CONGRESS caused the collapse of the credit industry.
I have my doubts if the much larger "loans" (that look more like gifts at present) to banking entities are as likely to be repaid; but I see littel resemblence between the two cases.