The issue is that most people use bags designed as fashion accessories rather than for carrying stuff. If you have a decent backpack, you don't really feel the weight under most circumstances. There are some exceptions, such as when you are carrying a lot of other equipment or taking extended trips with carry-on baggage only. Most of the time, it doesn't matter whether a laptop weighs 3.5 lbs or 3.5 kg.
That is the issue. Walking (or running these days) through airports, train stations, buses, etc. with a heavy laptop with a heavy charger in a bag on one shoulder is not healthy. It creates torque on your spine with each step. Do this year after year and the damage builds up.
There are ways around this.
While most people consider the weight of the Mac or whatever accessories being used for that Mac as the weight they are complaining about (most of which is out of their control; they bought the laptop that has that weight), what they can control is the weight of the bag or backpack being used. Take for example, Swiss.
Most of their bags that they gear towards laptops, especially in something that would carry a 16" laptop weights roughly 6lbs. Most of their "smart" bags that may carry up to a 17" laptop will weigh 3lbs to 3.5lbs...
.. For a bag alone to weigh 6lbs and then have to carry a 3lb laptop? You can't control the weight of the laptop, but you can control the weight of the bag you choose to put the laptop in. And even with that, 3lbs is a lot, and that's for something clunky like Swiss. There are others, and they are similar in size.
Now I have been using a bag like this:
The funny thing on this:
IT IS A DIAPER BAG.
Yes, a diaper bag I've had since our son was born. Instead of putting his cloth diapers, milk for feeding, any infant's snacks, etc., in the bag, I'm able to put my 13" MBA, all applicable power cords and charging bricks, a hidden pocket for my iPad (where normally a changing pad would go), and still have room for my glasses (separate pouch for them in the bag) as well as a lanyard for any badges or car keys to attach to. And this is a full 1.25lbs lighter than the lightest SwissGear bag. You know diaper bags have to be light to carry all of the things a new parent needs for their infant.
And to top that off, I was able to put my wife's 2019 16" MBP into the same bag. I didn't really feel the difference between her MBP going in and my MBA, and my MBA is a good 8 years older (back to mid-2011).
Now, granted that this is a near 10 year old bag, but they still make these in different patterns and colors; additionally, while I know I'm paying more for the bag versus running out to a tech store or somewhere new/modern to buy a bag that fits today's age, I'm not sacrificing what is cheap and/or convenient for weight or portability, especially when I have something that is lighter that can carry the same amount of things that the tech-oriented bags are designed to carry.
So if you can control the weight of what the MBP can go into that will make the journey with a 16" more enjoyable.
BL.