#so stop

To explain: Lucius has shown over and over again he's the kind of man who will use and manipulate anyone regardless of class or blood-status so him keeping Snape close as an older teenage boy makes complete sense to me. He sees Snape as an exception to the rule. That yeah, Snape may be half-blood and poor but he's brilliant and he can use that.

Regulus on the other hand is soooo far into Voldemort's work already, as shown by what he puts up in his bedroom of all places (holy shit), that I think Regulus wouldn't dare to see Snape as an exception. I think he would be disgusted by Snape and if he had any idea of Snape being basically a prodigy (I believe he didn't or if he heard of it from other Slytherins, wouldn't believe it), he would be disgusted that brilliance would be wasted on someone who he considered barely half a wizard and half a human since Snape is so poor.

Lucius may have been, even from a young age, a rich bigot but he has shown time and time again that he will put himself before the cause. Yes, he believes all those who aren't pure-blooded are beneath him but when it comes to his own skin and uses, that will always come first. Based on what we know, Regulus - both as a young Voldemort fanboy basically and even in his death - puts a cause before his own life. He would refuse to see anyone but Voldemort as an exception, I believe, because the cause is everything. Lucius sees that he and thus the cause can get something out of Snape - the way most hate groups prey on young men and boys from poor situations, and even on boys who are part of groups they set out to hate. Regulus, in my opinion, would be horrified that Lucius kept him around.

Don't smoke kids.

Astarion is pansexual.