A major limitation of naturalistic observation is that

The major limitation would be: not all children have the same opportunity to display a particular behavior in everyday life

Natural observation aimed to find certain explanation for social occurence by observing their behavior in their natural environment.

This method of course couldn't be done if certain group do not possess the freedom to act like other members because of their special circumtances (for example, poor children may expected to obtain part-time job on earlier age)