Continuity mistake: When Prue talks to Piper after stopping her phone conversation, she tells her that "the Sin Balls work a lot faster than [they] thought. Once infected, the victim only has a few hours before it drives them to total self-destruction." However, this is almost verbatim what was written in the Book of Shadows. It could be easily read by the viewing audience when the book entry was shown. So all three sisters should already know this.
Continuity mistake: When Prue telekinetically moves the sin ball box across the street she moves it ALL the way across but when the man infected with greed goes to get the box, the box is only halfway across the street.
Continuity mistake: When Prue and Piper leave to help the hostage, Piper asks Leo, "Do you think she's mad?" Her hair is in front of her shoulders. Immediately afterwards, she sits on the couch with Leo. Her hair is behind her shoulders.
Continuity mistake: During the scene where Piper is ordering merchandise from Bloomingdale's and Prue, she and Phoebe realize the "sin balls" infected them. Piper's hair constantly changes from being in front of her shoulders and behind them.
Other mistake: At the start of the episode when Prue and Phoebe are walking down the street (just before they find the box), the person with the green jacket on (in the background) reaches into the homeless man's hat and just "scrapes" the bottom of it. Not putting any money in, or taking any money out - a completely pointless action. (00:02:05)
Visible crew/equipment: After Lukas kills the other demon so he can move forward with his plan to go after the witches, when it cuts to the manor's foyer as Prue and Phoebe walk in, the green T-mark is visible on the rug at the bottom of the screen. (00:08:15)
Answer: That was a mistake in the series.
Also, the episode is called 'Babies First Demon' and this alone tells us that it's Wyatt's first time in the field (so to speak) and as the sisters say, they've done a good job of clearing up their own magical messes so far. Nobody really knows how advanced Wyatt's powers are, or will become. That's why the cleaners appear, to nip things in the bud. The Cleaners didn't want to chance that the sisters could clean Wyatt's magic up, just incase they couldn't. Therefore intervening themselves, just in case.