Are there any writers about dragons here? Speak up dragon writers lol.
Me!
First and foremost I think a lot of folks, readers and writers alike, are captivated by dragons because they represent the fantastical- everything your parents said didn't exist as a kid that you never really stopped believing in, or never wanted to.
That said, I really write two kinds of dragons. In some settings I present them as formidable antagonists, as they have been in mythology and fiction for centuries. Here sometimes the allure is in how big and frightening they are compared to the hero, as a character who can slay a dragon and not pee their pants isn't someone to be taken lightly. Sometimes it's in what they symbolize- they may represent some abstract evil, or the sheer power of nature (earthquakes etc), or the MC's biggest (literally!) fear.
But mainly when I write dragons they are intelligent (though still fierce), capable of communicating with humans beyond a growl, and capable of forming bonds with them. Here, a bonded dragon balances out the character they're paired with; mild-mannered protagonist and aggressive, blunt dragon, or grouchy MC and bubbly dragon, etc. Think of Jungian concepts (animus/anima for example).
For loves of action, combat on dragonback is exciting to write or think about because the rules are so different from hand-to-hand, on horseback, trench warfare, etc.
And if you like visual fantasy, dragons can be pretty, shiny, colourful and all that jazz. A guilty pleasure of mine, I must say.
I'm sure there's more, but the overall point is that they're such a pervasive and enduring subject/concept and a lot can be done with them.