Why? They don't bite, or sting. And are wonderful to look at.

Around 1980 I had them race, escorting me, while I raced through the forest on a road bicycle. At around 50 kph, them following me like on rails, maybe half a meter from my face.

Really big, maybe half or a third of that size, in many different shiny color patterns.

They were curious, but not aggressive. Was fun having them like a halo around my head :-)

While they don't sting, a 45cm long dragonfly would have some pretty gnarly mandibles, and could bite if it decided you were a threat. Probably wouldn't be much fun.

But they didn't. Maybe they would if you tried to slap them away, or otherwise make movements which they percieved as threatening.

As it were they were just curiously following me because of my speed, maybe even had fun doing so?

That didn't happen if you'd just walk, or jog along that place. Then they ignored you.

I have no idea how much that is so it doesn't terrify me, but a 47 cm dragonfly is terrifying!

18 inches is 45 cm 72 cm is 28.3 in.