Pink Vase

The useful part is that a placed one counts as a bottle. Any potion recipe that wants a bottle sitting on a table will accept it, so an alchemy bench can have the crafting station it needs without a plain glass bottle parked there looking like a placeholder.

That is reason enough to keep a few even if you never decorate. Clay is effectively free once you find a bank of it near water, and turning some into vases lets every table in the base double as a potion station.

If you are converting clay into coins, this is not the best conversion on current versions. Clay Pots need fewer blocks each and come out ahead per block spent. The ratio ran the other way on the old handheld builds, which is where the reputation for vase farming came from.