Good points, Joe.
I think we travel the same way. Each to his or her own, of course, but like you, I too travel with just one carry-on, and I think it's just so much easier that way!
I like the flexibility of being able to just "get up and go", and hopping off trains or buses at intermediate stops just because I see something interesting -- without worries of needing to find a hostel first and unloading a huge pack. To me, this trumps the rather dubious 'flexibility' of "having everything at hand".
I take a slightly different tack in dealing with "slashers" and other trials of civilization. I used to take my EC carry-on pack, but found that it was still too large -- where bus drivers often insist that it be relegated to the rooftop luggage rack or bottom cargo hold of the bus. Rather than choosing beefy packs, I now use a bookbag -- small enough that I can take it with me into buses, boats, etc. Even though my pack weight is only around 11-12 lbs., I still sewed on a hipbelt -- just in case I pick up heavier souvenirs along the way...
But the above works for me because I don't also pack camping gear for my travels.
Curious, Joe, where do you hail from? I live in Pasadena... home of the soon-to-be-rained-on Rose Parade.