Usually association rules algorithms present too many rules to be processed by humans. Some post-processing methods are needed which would filter out the "interesting" association rules.
An association rule, A Þ BC can be interesting if p(BC/A) differs greatly from p(B/A)*p(C/A). If p(BC/A) is approximately equal to p(B/A)*p(C/A), then the information presented by A Þ BC is likely captured by A Þ B and A Þ C already. So A Þ BC might not be interesting.
In this case the complex rule, A Þ BC is not necessary as the information portrayed is easily seen by much more simpler rules, A Þ B and A Þ C and people are usually more familiar with simpler associations rather than complex ones.