After a quick google, I have determined that a steel drum costs about £100. A beginners' set of Northumbrian small pipes will start at £500. Not to mention the cost of maintaining the instruments, which is far more complex than with steel drums - the expense of maintaining large numbers of instruments is what actually makes ensemble music cost-prohibitive for many schools.

Not to mention the difficulty of playing the pipes, which requires a level of musical ability not really required for the steel drums. in other words, if you are going to learn to play in an ensemble at school (ie, without your parents forking out for lessons and committing to making sure you practice at home) you need an instrument which is relatively easy to learn. Things like steel or African drums, through their very accessibility, offer an opportunity to make music for many kids who have not been fortunate enough to receive private musical tuition (and all instrumental tuition is private these days, in that parents have to pay).

So there are your reasons, Wavey. And please don't start arguing with me - this is my specialist subject.