If you knew a person committed suicide in your apartment, your mind might dwell on that, you might experience what some psychologists call "intrusive thoughts" of how they died, what caused them to die, the effects their deaths had on their families, maybe of your own death or that of your loved ones, or of their potential suicide, etc.
How many people want to be reminded of that every time they come home, or when they see their family resting or playing in their apartment, or when guests come over and the subject of their apartment comes up, or when they just reminisce about its history?
Many people actually know someone who's committed suicide themselves. How many of them want to be constantly reminded of that?
Such reluctance doesn't necessarily have anything to do with believing in ghosts.
On the other hand, there is something known as the "contagion heuristic"[1], which is "a psychological heuristic leading people to avoid contact with people or objects viewed as "contaminated" by previous contact with someone or something viewed as bad". There's also the "law of contagion"[2] which is "a folk belief axiom found in magical thinking which suggests that, once two people or objects have been in contact, a magical link persists between them"
[1] - https://en.wikipedia.org/wiki/Contagion_heuristic
[2] - https://en.wikipedia.org/wiki/Law_of_contagion