Rna viruses require their own supply of certain enzymes because

Host cells lack various enzymes that can replicate the viral genome of RNA viruses.

Explanation:

RNA viruses (like HIV) first need to convert their genomes into DNA by reverse transcriptase (RT) enzyme, virus supply reverse transcriptase enzyme own-self because host cell do not contain RT enzyme.

This DNA is then transcribed into mRNA that can be translated into viral proteins. So host cell lacks many of the enzymes like RT and protease etc which RNA viruses require.