I think the response isn't about simply weight-watchers, but it comes from hearing those that DO choose lightweight keyboards CLAIM that it comes with no penalty... Basically, as if to say that those of us that DO appreciate a good 76 note keybed, high build quality and TOTL features have no idea what we are talking about...
I am the first to say that, if you need light weight, for WHATEVER reason, go ahead, best of luck, mate! I am pretty sure that by the time I get into my sixties (got another ten to go!), I may have to use lightweight equipment myself. But there is no way I will try to tell anyone else that, just because it is MY choice, it MUST be the best way! I will look enviously at other player's rigs, with nice big actions, and wish I could still lug one around

There is a reason that you don't see the majority of pros on TV or in Vegas, etc., playing one 61 note ultra-light workstation. It is NOT because they can afford to play anything they want to, it is because they need a keyboard they can play ANYTHING on, from full piano parts, to multiple splits and run the whole show with midi. 88's are the norm, then 76's, and most of the time you see a 61, it is because they have more than one keyboard in the rig (which kind of defeats the whole point)
Now SOME of them get cartage (but fewer than you would expect), but to most pros, the one area they CAN'T cut corners on is their rig. If they get a call for a piano part, they daren't show up with a 61, no matter HOW good the sound.
My arranger gets used for everything from standard arranger gigs, all the way up to full band calls and session work. It replaces two keyboards and a module or two (for full band gigs), and so is MUCH lighter than previous full band rigs. It replaces, from WAY back in the day, a van full of Hammonds, Rhodes's, Wurli's, Yamaha's and the like.
But, apart from the B3 section (and what IS a reasonable replacement for one of those to a diehard Hammond fan?

), it performs as well as all the other stuff, at a fraction of the weight. But to my ears and fingers, this is the lightest it CAN go at the current time without me noticing a REAL drop-off in quality.
I have always said, as soon as they bring something out BETTER that is lighter, I will get it in a flash. As long as it doesn't bounce around while I play it because it is TOO light! But the MINUTE it involves any compromise with the key-action or sound, sorry, got to pass...
Until I'm too feeble to move it around...