I actually prefer using just a MacBook Pro in the overwhelming majority of situations.
I also connect all of my peripherals through my OWC dock and have a single USB-C cable to connect/disconnect depending on whether I want to work at my desk or elsewhere.
There are certainly pros and cons, however for my workflow/budget I find this approach makes the most sense.
It is less hassle not having to keep two systems in sync, updated, backed up, etc, etc. My work in Lightroom Classic is more straightforward since I don’t have to sync my catalogs (I know I could keep the catalog on my external, but I keep it on the internal SSD which is faster). Also, some software requires additional license purchases to run on multiple machines so I avoid that problem as well.
The biggest con (for me) is not having a system to use in the event my MBP should need repair work. I have always thought the iMac was a very nice machine and in a world where money was no object, I would probably buy one (who am I kidding? If money is no object, give me a loaded Mac Pro). However I think if I am ever confronted with being without my MBP for a short period, I will probably add a Mac Mini that I can connect to my desktop setup.
One other case I would have for a second Mac would be if I can ever convince my wife to migrate from Windows I will buy her whichever laptop she wants!
There are times when I see how fast certain files render on some desktop Macs and I am really tempted to upgrade…but this is mostly for household/hobby/semi-professional work! Since it’s not really a paid gig it makes it a bit hard to justify getting too carried away! (He says smiling, as he is opening the box that just arrived with his brand new AirPods Max!)
Edit: Seeing some of these other posts with images of older computers sent me to the archives to dig out an image of my first computer! Obviously this was NOT an earlier laptop, however after a few years of using this I never wanted to be tied to a desk again! LONG LIVE THE LAPTOPS!