I think your opening comment is best. All companies may not "scam", but I believe that nearly all "take advantage" of infrequent renters. Add to that someone visiting the USA from abroad, and it only compounds the "scam".

As for tracking your flight, how is Dollar (or any company) going to know that you are actually on that flight? Maybe you were bumped? Maybe you changed your plans and neglected to cancel your car reservation, especially since there is no credit card guarantee?

I make countless alternate reservations all the time. I may have 5 or 6 depending on my plans and the funky rates I find. I do my best to cancel out the ones I truly do not need, but I also have flown into a city and had multiple reservations with up to 3 different car companies. Sometimes I won't know until the morning of my flight whether I need a 1-day rental, a 3-day rental, or a weeklong rental. Since the companies often DING you for changing AFTER you pick up the car, I'll lock in a good 2-day rate, another reservation with a good 3-day rate, and maybe a third reservation with yet another company.

Car rental agencies are all about yield management. Lots of no-shows will happen sometimes. And sometimes, everyone shows up.

If you had belonged to the Dollar Express program (which is free), they may still have tried to manipulate you. I tell every single person to enroll in whatever frequent renter program they can find. You generally get a separate line, a decent upgrade, and most importantly, some respect from the clerks -- many times it is the station management who "work" the Express line and not the I-need-a-commission-badly rookie employees.

The Hertzies hijacked this post and I agree with most of what they said. Again, being part of the #1 Gold Club yields great benefits, although I sure do prefer the option to select "any car" with National (Emerald Club) and Dollar (Dollar Express).