Why was Jaime kept on as a kingsguard?

[Tini]

On ‎10‎.‎11‎.‎2016 at 8:10 PM, Jaak said:

Robert did not make Stormlands a crown property either. He gave away Storm´s End to Renly for good - Renly could have married and left Stormlands to his children, while Robert wasn´t keeping it for his future second sons.

Dornish held such a belief after Tommen was King. They thus held an expectation that King Tommen would not hold to an additional lordship inherited from his mother, but give it away to a suitable family member, like Myrcella, like Robert had done.

No, the Dornish did not - they intended a coup at the time. They claimed Myrcella was the rightful queen because she was the firstborn, so it would've been the other way around: They expected Myrcella to confirm Tommen as Lord of Casterly Rock.

[The Frosted King]

Jaime was kept on the Kingsguard for the same reason why Moat Cailin was never rebuilt, or another fortress established that would serve a similar role.

Plot.

It needed Jaime to have close proximity to the throne so as to be able to do his part in making his three treasons, just as Cailin needed to be a ruin vulnerable from the north so the Ironborn could snatch it, and doom Robb Stark, even though fortresses that played similar roles in other kingdoms ala the Golden Tooth or the Bloody Gate are held in tip top condition, because they're vastly important.

Same reason why Rhaenys was murdered, rather than kept alive to unite the claim of the old dynasty and the usurpers, as what happened many times in real history.

Even in canon, why would the Boltons marry a fake Stark rather than just kill them all off and claim Winterfell, as Robert did?

Why did Orys Baratheon bother to marry the Storm king's daughter, rather than murder her and reward another Targ supporter by marrying their sister/daughter, etc?

Plot plot plot plot plot.

Jaime breaking the cardinal rule should've seen him cast far from the order, at the very least. No amount of angry Cersei-isms should've defeated that notion, but apparently nobody in the capitol thinks about anything aside from feasts and parties.