This could be for any number of reasons: Most likely because it's a lousy song request, we might not know it, it could be a flat out terrible request, we haven't found the right spot for it, half the room would go home if we played it, or it could just flat out suck really bad. If you are really that concerned please feel free to aproach the stage and engage the perfomer who is not currently mid song delivery and they will help you out with your written request that most likely is a waaaay below average judgement call on your part.