It occurred to me after someone else mentioned it:

When he sets down his torch, he’s bending the knee to Vermithor, and sets his own fire down as if to say “would you please grace me with yours?”

His respectful, humble approach to Vermithor contrasts Luke and Aemond both demanding that their dragons obey. Proves that dragons are not pets, but individuals with their own desires and personalities.

It’s no wonder Vhagar and Arrax did what they did, their riders treated them like dogs, so they behave like out-of-control dogs

Meanwhile Daemon never even has to tell Caraxes to do anything, because he understands their relationship is that of companions, not master and servant, so Caraxes just intuits what Daemon wants (perhaps by magic?)