Severus Snape in ten years might dig his heels in and argue, or try to ensnare him in the verbal art that left him alive walking the line for so long. With more experience and a closer endgame, he'd be inclined. All or nothing.

Now, he's just used to being put aside until someone needs something, too disillusioned with the world at large to have any desire to try with someone from home. He doesn't even think he'd have a better chance with a person (like this) further in the corner of the Dark Lord than out of it-- both factions hate him equally. And why not?

The question comes and he's not surprised, doesn't even turn around. Severus was so offensively presumptuous a moment ago but, of course, Draco Malfoy will need something from him. That's how it works.

"I told you that I'm the head of the Xenobiology and Genetics department. I have patients, I have projects. I have this ship, which sees fit to slowly consume us."