I don't have the new body style of Macbook, I have a 2015, but I can tell you that when I switched from a PC laptop to the 2015 Macbook, it was thin enough that I could now travel with my laptop and an iPad in my carry-on. Before I had to make the choice of carrying only my laptop or packing a roll-aboard to be able to fit everything I needed for a work trip.
What does a thinner laptop enable you to do? What a question. Might as well ask why compact cars are more popular in the city than pickup trucks.
I had a similar experience back in 2012 when I bought a 13" MacBook pro after carrying around a PC laptop.
But, I wrote "at this point".
Does 3mm, at about the same weight, really make much difference?
I suppose incremental improvements(?) in "thinness" accumulate, and in 2028 we'll all be complaining that the new MacBook Pro at 2.8mm thick is easily bent and has no ports.
"At this point" does a marginally faster CPU make a big difference? Not to me, my "workhorse" laptop is a 2013. But if they stuck with a 2013 CPU in a 2018 Macbook, people would go ape shit even though for people like me, the faster processor doesn't change a single thing about how the machine works.
Way too often people on here see something and think "that doesn't help my use case, therefore it's a stupid decision" and never stop to think "hey maybe someone has a use case I don't have, and maybe this helps them". To you, 3mm doesn't sound like a lot. To me, a few hundred Mhz or another few GB of RAM doesn't sound like a lot. But you don't see me screaming in the comments thread "how dare Apple put a faster processor in their Macbooks instead of shaving off another few MM of thickness!" because that's just ridiculous. Someone out there is happy that the machine is faster, even if that person isn't me. I have the ability to put myself in someone else's shoes and be happy on their behalf.
Some people's laptops sit on a desk all day and that's fine. Mine doesn't, and every MM shaved off is another pair of socks I can pack into my luggage.
Always with the hyperbole. How would you feel if your laptop suddenly increased 2mm in thickness but didn't gain any weight? Most people wouldn't even notice the difference if you didn't point it out to them.
At this point, what are the benefits of a thinner laptop? Lighter I can understand, but what does a thinner laptop enable you to do?