Bran Stark created a new seal

Why do they still use gold dragons as currency in Westeros? [Duplicate]

This gets complicated, but that's the nature of A Song of Ice and Fire. It goes without saying that this will contain spoilers, I will do my best to mask them appropriately.

Robert didn't hate Targaryens

Not in the classic sense of "they must all die". His rebellion was sparked by the actions of two specific Targaryens, namely Rhaegar and his father Aerys II.

In particular, Rhaegar ran away with Lyanna Stark, the sister of Ned and Brandon Stark and Robert's future wife. Brandon went to Kings Landing to get his sister back and was captured by Aerys. When Rickard Stark was called to Kings Landing to release his son, the king brutally murdered his father and son. At that time, Aerys demanded the surrender of Robert and Ned, and Jon Arryn of the Valley, who was tending the men at the time, raised his banners in an uproar.

What does this have to do with the fact that Robert doesn't hate Targaryaner?

Much.

A Clash of Kings and A World of Ice and Fire say Robert's grandmother is Rhaelle Targaryen (that's important and I'm getting to the point).

Why is it important and haven't we talked about money?

I come there. It's important because while anyone (Jaime Lannister, Ned Stark, etc.) could have ascended the Iron Throne, every claim would have to be legitimized. Robert's claim was easy to legitimize because

Rhaelle was the daughter of Aegon V, which made Robert a direct descendant of a Targaryen king and gave him a blood claim to the Iron Throne - as long as no other children of Aerys II were alive.

So his claim was only valid as long as he was the most suitable family member. Viserys and Daenerys both had a stronger claim to childbirth, which is why Robert wanted them dead.

Out of love for all that is sacred, I asked for coins!

I told you I would get there. Robert kept the Targaryen Dynasty currency intact because he was something of a member of it. He did not implement a new system, but continued the old one under new management.

This was important as many Westeros homes supported Aerys and his children. Replacing each dragon with a stag would pour salt into a fresh wound if it needed the support of the Great Houses to consolidate its rule.

Additionally, the only banks (book or TV show) mentioned in the series are in Essos. The Westerosi seem to like to hang on to their money, which means that to replace coins, someone has to go from house to house, village to village, kingdom to kingdom from thorns to the wall, exchanging ANY gold coin in seven kingdoms.

At the end of the day, gold is gold and it would have been politically and logistically difficult to trade dragons for deer.

Gee Whiz

@Hamlet you should probably post a link to the scene in question. I just looked back at a few and most likely pointed out that Robert hates Targaryens when he talked about Daenerys and Viserys. He talks about what her father and brother did during the war and says he'll kill any Targaryen he can get his hands on (presumably without himself, Renly, and Stannis - not to mention his kids, all of them Have Targaryen blood). The scene discusses a threat to his rule that doesn't obliterate an entire bloodline of hatred. As my answer says, he was angry with Rhaegar and Aerys II.

Skooba

The full quote reads: "I'll kill every Targaryen I can get my hands on until they're as dead as their dragons, and then I'll piss on their graves." seems pretty hateful from the whole family.

Skooba

Also: Ned didn't pretend to be surprised; Robert's hatred of the Targaryens was madness within him. He remembered the angry words they'd exchanged when Tywin Lannister had given Robert the bodies of Rhaegar's wife and children as a token of loyalty. Ned had named this murder; Robert called it war. When he protested that the young prince and princess were nothing more than babes, his newly built king had replied, "I don't see any babes. Just brood dragons." Even Jon Arryn hadn't been able to calm this storm.

Skooba

So also: "And how long will this one remain innocent?" Robert's mouth hardened. "This kid will spread his legs and breed more dragon brood soon enough to plague me."