The prehistoric squawk

What a glorious day it was today. Blue skies and warmth in the sunshine. I was down at Newark Castle first thing, the tide was out and crab fishermen were checking the tyres they leave in the silt that crabs crawl into and can't escape. There was a nice bit of birdlife and this grey heron was bonnie as it flew mirrored along the clear blue of the water. There are quite a few of them along the shoreline and a heronry just across the M8 among the trees.
I'd been talking about grey herons at the weekend with my pal when we were out walking around some reservoirs just at Hadrian's Wall walk. One had just lifted from the water and I'd said how prehistoric they look, and my pal had replied that they did indeed look reptilian particularly with the rasping squawk they make. That made me chuckle about another point he'd made a while ago about dinosaurs.
Why is it that T-Rexes are always depicted on tv and in films as roaring lion-like when they are reptilian? The sound a heron makes would be much more likely than the deep-throated cries that are used. In school when children play with dinosaurs they always imitate a roar!  
Anyway... a lovely day by the water my head full of these important thoughts.