They are constantly bringing people lost back because they happen to still be in the pattern buffer but if someone else is with them they might over write whoever was in there last, in other words O’brian is about to arrange a transporter “accident” he’s not going to stop you from going with them but he is going too give you the best chance to survive… since he likes you.

I also just had this thought, what if that is why there are so many “accidents” on the enterprise he has secretly been a serial killer this whole time started small with transporter accidents but then he got promoted to chief engineer so he moved on to holodeck incidents and unfortunately timed warp core malfunctions.