I honestly can't see the weight being a problem for a lot of folks if they use a hipstick and a guide arm.
I currently push a 21 x 17 SEF all day which weighs over 1.2 Kgs, although I admit I only go out every couple of weeks or so and there's no way I could swing it day after day if I was prospecting daily for a living, or for days at a time on holiday. I need some time to recover even with the hipstick and guide arm, but then I'm 56 years old and that may have been different 20 or 30 years ago.
Maybe also that weight could be the lesser of two evils for people who have older model detectors that don't have the smooth timings that say a GPX 5000 has?