The usual culprits are virtual machines, large images, video editing. A little less common: big data, large matrices, scientific computing in general.
I never hit 16 GB on my laptop (I even disabled swap) but I got close once with three browsers open (I segregate some web apps into different browsers), a few VMs, some other random application running. It made me think if it was time to buy the extra 16 GB I can fit into my laptop. I just checked, it's about $100.
For sure, I regularly sit between 12-16GB used (mainly doing web development + docker work, large systems, many services), but frequently will be above that when running a lot inside of VMs.
You are also up against a loosing battle of programs using more RAM to do the same job. You get a better experience now, but you can also expect normal PC usage to result in big RAM usage.
I never hit 16 GB on my laptop (I even disabled swap) but I got close once with three browsers open (I segregate some web apps into different browsers), a few VMs, some other random application running. It made me think if it was time to buy the extra 16 GB I can fit into my laptop. I just checked, it's about $100.