How useful are the keywords having a search volume below 1000 in my PPC campaign

if these keywords have relevancy then we can run a campaign on low SV keywords.

We can launch a campaign on low-search volume keywords if these keywords are relevant.

They are useful in the initial stages of product launch, as these keywords will have (supposedly lower competition and bids) so you can start with aggressive bidding to get ranked and start to generate organic sales through these keywords (as it was the case with one of my product that generate more sales from a 1500 volume keywords in comparison to the main keyword), if you organically rank on these you can not only get organic but PPC sales which can lead up to you ranking on main keywords as well.