Trivia: Holly Marie Combs's real life pregnancy with her son Finley Arthur Donoho was mirrored by Piper's pregnancy with Chris in this season.
Trivia: In this episode we see Bianca as a little girl, and she looks about 6 yrs old. If Chris isn't alive as a child yet, this means that in the future Bianca is about 6 years older than him.
Trivia: Chris' role this season (specifically, his traveling to the past from the future) was originally intended for Wyatt. After deciding that Wyatt coming back from the future is what viewers would expect, Chris was created and introduced instead.
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.