Draconic tribes focus more on gaining lots of tributes, then feudalising with their special decision, which instantly vassalizes all of their tributes rather than normal tribes use of conquest CBs.
I am considering changing the mechanics of vassalizing tributes. An option I'm considering, which I have tested before while they were in development, is that when a ruler dies, their heir can chose whether to remain a tribute, pay a lump sum to get out of it, declare war to get out of it, or become a vassal. The suzerain would not be able to declare a war to force them to become a tribute. I originally didn't like it since it felt rather random and didn't give much feedback ahead of time, but I think I can use a modifier with a tooltip to give the information.