Whilst I agree that Rex's load factors are low, it needs to be mentioned that the promo fares require passengers to pay $6 for seat selection. For some, this is a cost they don't want to pay.
Rex's booking system does not assign a seat to those who don't pay until check-in. All seats are available for passengers who pay for a more flexible fare, legroom seats or $6. Therefore, snooping at seat maps isn't portraying a completely accurate economy figure.
Touching on the topic of load factors. I believe it's completely far fetched to think Rex will fill their 737's consistently from day 1. It takes time to build a customer base, especially when most who aren't from country ports don't know who Rex are (yet). They are beginning to advertise (perhaps finally forking out for a marketing department now PAG have board members), which will see pax loads gradually increase.
It cannot be forgotten that COVID is still around with lots of uncertainty up in the air. I'm interested to see what happens with these 800,000 1/2 price flights now that Queensland have another community COVID case.
Not helping Rex's cause is the fact some booking sites (exclusive of Webjet) don't actually advertise Rex's lowest fare. Comparing flights in a weeks time, VA was the suggested airline with Rex coming in 3rd behind Jetstar due price. When looking at the respective websites for the same date and flights, Rex were in fact the cheapest by a few dollars, however the comparison site did not advertise Rex's promo flights. This is true for multiple websites.
Most mum and dads aren't aviation fanatics and therefore may not book from the airlines website and book simply from the cheapest fare available upon instant comparisons. If these sites aren't actually showing Rex's cheapest fares, they are potentially losing a lot of customers for no reason.