is it simply another sign of Roberts incompetence that he didn't demand that the houses that fought against him the rebellion surrender hostages to the throne. Such as Garlan Tyrell?
No, I think Robert actively did that to promote reconciliation between the loyalists and the rebels. What’s more, it worked. Compare the paranoia after the Blackfyre Rebellions (”red or black was a dangerous question”) to the unity after Robert’s Rebellion (”a maiden could walk down the Kingsroad in her name-day gown”) and you can see the difference.
my favourite thing about jon possibly having a targaryen name is that when lyanna told ned he was probs like ‘… ok sis that’s cool but…. how the fuck am i meant to hide jahaerys jacarys jalapeno the third from robert with that name?’
Which is the bigger number, five or one? [holds up his left fingers] Five… [clutches his right fist] …One. One army, a real army, united behind one leader with one purpose. If the Dothraki horde crosses the Narrow Sea… we won’t be able to stop them. - Robert Baratheon