Direct biceps work just doesn't do a whole lot for long term growth. It makes the biceps look nice but if you didn't do them for a year and came back and put in a solid few months, they'd be exactly where they would have if you did.
So there's a lot of people in this forum who've tried not doing them and either grown their arms, had them stay the same, or in some cases had them shrink a bit for a period and then build back as their lifts increased (usually because their biceps or triceps overshadowed their primary muscles in rows or benches which ain't exactly something good). The overwhelming thing is though, that most found their arms eventually come back bigger and that they weren't really losing anything or having their arms attrophy to nothing leaving an irreparable deficit. Just some basic work to bring them back up and maximize the base.
So there's nothing wrong with direct training - go ahead, a lot of people like it, but it shouldn't interfere in any way with the big lifts because this is really where that growth is going to come from. And if they are a weakpoint to a compound lift, then certainly train them. It just depends on your goals, if you like having a nice pump in your arms and feeling that you've worked them, do it up.