The analogy with egg collecting doesn't really stand up. Every egg you collect is a bird that might have hatched. That's got no parallel in song collecting.

A much more apt metaphor is that of a seed bank, which exists to ensure that the seeds of plnats are available to be planted again when the occasion arises.

The real danger - if such a word is appropriate in this context - is the one indicated by Malcolm, of the range of songs in use being whittled down to merely those which get recorded by the right people and distributed by the right channels. This is the same process that occurs in industrialised agriculture. A seed bank is some kind of defence against this, and a collector of songs provides the same service to future generations.