Here's why:

* rRNA is the structural and functional component of ribosomes, the cellular machinery responsible for protein synthesis.

* Ribosomes are incredibly abundant in cells, especially those actively making proteins.

* rRNA accounts for around 80% of all RNA in a cell.

While other RNA types like mRNA (messenger RNA) and tRNA (transfer RNA) are essential for protein synthesis, they are present in significantly lower quantities compared to rRNA.