Honest question about PP400 preamp

This has been driving me nuts, but I don't understand why so many preamps, including this one, don't come with a volume control.
What would be a better option? Right now I have my turntable connected to the PP400 and then to a audio card (using the preamp inputs on the Behringer UMC204HD) then to Sennhiser bt100 to output to some speakers I have setup.

As you can tell from this description, it's far from optimal, it's working. But I really want to simplify this setup and I don't know how.

Speakers are setup quite far from the turntable setup, so the bt100 is there to send it out (I don't know if that is an issue).