Exactly. Most probably come from a Windows world, where memory management sucks, and the OS eats every available free byte of memory by design.
Realistically, I think Windows is quite a bit better on memory utilization at this moment.
I have a 2010 MBP with 8GB of RAM and El Capitan is performing pretty poorly, especially when I start really getting into a workflow.
But I can boot that same machine into Windows and have it run really well and not struggle nearly as soon. In fact, I often boot a lightweight Linux distro in VM from the Windows side whereas the OSX side has a really hard time with it.
I could put 16GB of RAM in since it's user-upgradable, but OSX only supports 8GB on my 2010 17" while Linux/Windows boot fine with 16GB installed. Just my rotten luck.
Having said all that, I'd like to see 32GB as an option since I don't know what my needs will be in the next 5-10 years, but if I'm going to shell out north of $4,000 for a laptop, I would like to be able to avoid that bottleneck.