Not everybody gigs... and not everybody is so weak they can't dolly a 50 lbs keyboard. Have you ever looked up the weight of some of the TOTL Kurzweil's? PC3K8... 54 lbs! No speakers. K2500X 72 lbs! No speakers.
Pros have been using these for decades. Heck we had a thread about the old CP70... and a whole bunch of guys hauled one of those. Over 300 lbs.
Basically, what something sounds like trumps its weight for anyone that CARES about their sound. But there are some here that don't even like the 30 lbs or so the T4 weighs... I guess sound is not THAT important!