I don't mind big watches, got a beautiful citizen Eco drive that pushes 45mm.
But the 38mm Apple watch is proportionally better suited to my wrist, and it feels like it counters that element of "LOOK AT ME AND MY SHINY NEW EXPENSIVE WATCH", because it's not so big that anyone who looks at your wrist will see Big Ben staring back at them.
If the band sizes were different, I would've bought the 42mm for sure, but I'm more than happy with 38mm after seeing it for real.