I get that it's really easy to be irritated with all this bureaucracy, and the constant appointments.
The reason I strongly in favor of a dating ultrasound in the OP's case is that her situation seems like one in which a planned c-section, possibly without trial of labor, will be on the table from the beginning. I know that TOL has some benefits to the baby, but it can also make recovery much harder, and complicate logistics for the family - if it were me in this situation, I'm not sure i'd be willing to do it.
That means that c/s will be scheduled for the best available estimate of the 39th week of pregnancy. Standard LMP dating is known to have limited accuracy - are your cycles exactly 28 days every time? What if you didn't ovulate when you thought you did? LMP dating can give you a due date that's seriously off. However, embryonic development moves pretty much in lockstep, so an ultrasound before the embryo transitions to fetus can give you a much more accurate estimate of gestational age, and hence, a better due date.
If you're planning to labor, a little uncertainty on the due date mostly means you have more NSTs, if your practitioners are into that (they're really not a bad idea for postdates, again, IMO).
If you're planning a c/s, this info can make all the difference between taking your healthy baby home right away, and spending some time in the NICU for iatrogenic prematurity, if at 39 weeks by LMP, your baby was actually more like 36 weeks. An accurate due date can also mean the difference between an uneventful surgery done by the doctor and anesthesiologist you choose, while your kids are happily ensconced with grandma; and a mad midnight scramble to get a sitter and get to the hospital so that whoever is on that night can get you into the OR as soon as possible. This is not as big a deal to me as avoiding the NICU, but having done that mad midnight scramble (by ambulance, DH had to wait for the sitter), I feel pretty strongly that it's not a thing to dismiss.
My dd spent a month in the NICU for unavoidable prematurity and the experience sucked, contributed hugely to PPD, and left us, as a family, more than slightly traumatized. I am grateful that we got a healthy daughter out of it. I will, however, always give advice that I think likely to help avoid the NICU.