You know what I find interesting? I walked past the same buildings sites aged 11-early teens and was whistled at repeatedly. Not every builder. But, and this is a big but, if it happened repeatedly, that means the whistler wasn't reported, wasn't had-a-word with, wasn't fired, wasn't thumped by the dads who were builders, wasn't taken aside.
The other builders heard it, saw me, knew what was happening. So even if every builder wasn't a pervert, and many clearly were for it to happen in more than one place, most of the builders didn't care enough to do anything about it. Which reflects my general experience. Hundreds of incidents of street harassment (some of it really unpleasant and sometimes physical), I can count on one hand the men who intervened, even to check I was OK. One of those men was a stranger who is still a friend to this day.
And in terms of numbers, somewhere around 1-3% of men find children attractive sexually. So yes, there probably is one on a decent sized building site.
The only time I've ever thought 'fair play' when harassed in the street was in another country, DH (who looks like a harder, taller Mike Tyndall) was with me, and it was a pure compliment, not creepy. I didn't feel unsafe and I over 30. Maybe that's a compliment, said honestly. That was not my experience as a child.