You can dock your laptop at work, then dock it at home, take it with you to a meeting room at work to browse supplemental materials and/or project your screen n the meeting, and use it for the occasional trip (like using it on the train to work).
It's not like you have to be on a plane for the portability to be useful.
I think the point of OP is that while laptops are fine for business trips, tethered usage is superior. My setup is a laptop. Both at home and as work I have a solid desk with an ergonomic chair. On the desk are thunderbolt docks, the docks have hooked the keyboard I like, 2 monitors on mobile stands. And that's it. I have most the advantage of a desktop while using the same machine. One cable to unplug. Super nifty.
Still, being able to take you laptop to a meeting to either project, or to look up related material to catch up and clarify before making a point in a meeting etc. is invaluable (no, working at a laptop during a meeting doesn't mean you're not paying attention, it often means you're cross-referencing discussions with other data live).
It's not like you have to be on a plane for the portability to be useful.