I never understood this mentality myself. I use parts libraries all the time.

Whether or not I drew the symbol, I still have to double check it as it's not like every symbol I every drew comes out perfectly the first time. So if I need to check it, why not save myself the step of drawing the rough draft of it?

For example I've never had an issue with a snapeda schematic symbol. Even free tier. Although sometimes I rearrange them for esthetic reasons. I've definitely had to adjust their footprints for DFM reasons. But IMHO it's much faster to tweak someone else's work than start from scratch.