It can be extremely lucrative to write hit. You can earn huge amounts of money with it, that is .... as long as it is copyright protected.
Things did not work out great with the revenues from 'Happy Birthday', but they did for the Netherlands' most successful hit: Venus by Shocking Blue forms the basis of the assets of composer Robbie van Leeuwen and publisher Willem van Kooten. Venus is based on The Banjo Song, which in turn is based on Oh! Susanna, a number dating from 1848.
Copyright holders can benefit from this success throughout their lifetime. Their heirs can also reap the benefits of their creativity. That is because copyrights on music only expire seventy years after the composer who is entitled to these rights passes away. This is also why a lot of classical music is royalty free. Big music companies are now lobbying to extend the copyright on music to a period of one hundred years to ensure that the rights on big hits from the Nineteen Fifties and Sixties will not expire in the near future.
In the Netherlands around 24,000 composers and lyricists have made arrangements for them to be paid royalties whenever their music is used. It gives them security as they swing their way into old age.