Pergamon additional Basilike Patris why in Sinope and Byzantion?

Why put the most important building for Pergamon in 2 insignificant eleutheroi controlled region? As Pergamon the natural expansion would be to go Anatolia and neither of these are parts of them.

Byzantion i could somewhat understand due to it's significance later but Sinope is just an insignificant backwater Hellen with little potential as capital that only matter to a more backwater Pontus.

Make it Sardis, Ephesos or even Ipsos since Makedon and Ptoleamy seems obssesed with Ipsos potential too now