Why don't vassals transfer trade power and ban you from asking them to transfer trade

[CaptainChiatrol]

Why don't vassals transfer trade power and ban you from asking them to transfer trade power?

I thought they did but then I checked and clicked and compared it to nations that are transfering trade power to me.

Since I'm banned from asking my vassals to transfer me trade power why won't they?

I don't want to have to integrate my vassal just to get all that free money.