This is in part because I switch between working from home and working at the office fairly often, have travel time in between, and need to have access to more VMs than I can fit on my laptop's internal SSD comfortably.
I also may have SIM cards rattling around somewhere; when I travel internationally, I buy a local prepaid SIM, and I may have older SIM cards left over from the last time I replaced one.
Exactly the same with me, I regret only getting the 256GB internal drive with my Thinkpad but I wanted the 2560x1440 so I had to trade something off (since it's a personal machine not a work machine), I suspect I'll be upgrading it before long.
My laptop bag right now contains, 3x1TB USB3 drives, a Thinkpad T470P, an iPad Mini-2, 4-5 4-16GB thumbdrives, two phones (Nexus 4 and a Moto G5 Plus).
Not a spy, just an enterprise web developer.
For me, someone who occasionally carries two laptops (bulky company-issue, light personal worktop) and a sundry of perboard assemblies that would make the TSA raise an eyebrow. But I think even that might count as 'unusual' if you're talking about the average population. How many peoples' jobs require them to occasionally have 24/7 access to their work computer? How many people carry around devices solely because they vaguely intend to tinker with them at some point, and you never know when you'll have a spare hour?
Probably less than 10%. Also, side-note, as much as I hate the TSA's security theater, I've never actually had problems with bringing things that look like bombs through security. Including a wired belt with a black box covered in electrical tape (compass)...good thing I'm white!