Why all of their screenshots are on laptops? Doesn't anyone use real computers anymore?
Fewer and fewer people. Given that laptops today can have 32 GB or RAM, Quadro cards and fast quad core CPUs, there's less and less work that requires a 'real' workstation. Even the CAD people where I work have mostly switched to laptops. (Full disclosure: I use a workstation as my main computer both at home and at work. My laptop is mainly for traveling and computing in the sofa)
To get laptop specs approaching my desktop I'd need to spend close to double the cost and I'd still be giving up quite a bit since there just aren't equivalent laptop-grade CPUs, GPUs, and storage options that compare.
Instead, I keep a desktop that's a bit lower spec than a serious workstation but higher than most basic office/home systems (i7, 16GB RAM, SSD, a couple of HDDs that were in previous machines, GTX 980, optical drive, etc) and a more basic laptop for use in less demanding tasks when away from home.
I guess my usage is a bit of a throwback in this sense but my desktop is the center of my home computing. Until recently it was the network storage for my media library (since offloaded to a NAS but still acts as the Plex server for transcoding and streaming media throughout the house). It's my main gaming platform. I use it for editing photos and video and well as my hobbyist-level dabbling in 3D graphics and animation. And it's obviously capable of all the less-demanding stuff like web browsing and Netflix on a decent-sized monitor.
A docked laptop would have lower CPU, GPU, and storage options and even if I bought some exorbitant "desktop replacement" model, it would cost a fortune and not be very portable. Much easier to buy a more reasonable notebook to take with me and even remote into my desktop if I really need to do some heavy lifting outside the house.