Thank you for this question!
I totally understand the 'no need to walk to the kiosk' and 'get a new fastpass immediately while in line', but I also firmly believe that the loooooooooong stands in line are part of the experience and I don't like getting my phone out for even a minute as that usually leads to "one more thing, wait, just one more....". I have been 3 times as an adult, twice with adult/near adult companions, once with 2 other adults, a 4yo, a 5yo, and an infant. All before MaxPass. There are no bad memories associated with any of those. The most recent trip was the year CarsLand opened, and Anaheim was having a heat wave. We went through the Radiator Springs full line 3 or 4 times, FP line once.
I am going back this fall with an adult and a 10 yo, his first memorable visit as he was the infant in a previous visit. I am only thinking about MaxPass for maybe the last day, but am not even sure about that.
Thanks for letting me ramble to folks who might get it!