You don't even have to be huge. If it's obvious you work out, sometimes people are just grossed out by your vascularity.
I'm not that big.... anymore.....but I have extremely low bodyfat and my arms are very veiny. Someone always says something, usually at a checkout counter... they don't really know what to think or what the implications are of what they are seeing...
They might say "why do you have so many veins?".... like they don't..
It's just not an everyday thing to see fit people, especially extremely fit people... and even more rare to see someone humungous and fit... not perma-bulked. Nobody really seems to look twice at permabulkers. I guess that would be considered more "common" almost like looking at a borderline fat person... which is the norm