Re ham radios on vacation - The Geek in me says it's because any new (to you/me) areas have different propagation properties. That and the 'fun' of trying to run portable equipment by tweaking it is like moths to a candle.
As for the underlying question of 'why when I am on holiday do I find it easier/more comfortable reaching out to others in the 'techno-sphere' versus interacting with fellow vacationers? I wouldn't presume to answer for you but for me it would be -
A) An innate shyness
B) Trouble de-coupling brain after 50 weeks on the corporate treadmill
C) A realization that I had little in common with fellow vacationers (you tend to see very few geeks slapping on the factor 50 and hanging out round the pool)
In short – I don’t know but you aren’t the only one (grin)