While I hear and read about presta valves with removable stems, I've never been aware of any that passed through my hands. What brands use removable stems? Is it something they use as a marketing tactic and have displayed on their box?
And why? Other than those using tubeless setups with the valve stem mounted on the rim, I'm not certain I see their reason for being. For tubeless, I can see why one might need to change a core if the sealant gums up the valve.
While I had a valve core remover for Schrader valves, the only use for it was to let air out quicker and more completely from larger tires and tubes that would take longer to empty of air to change the tire. My 25 mm tube doesn't need much time to empty.
Just curious. I'm not hating on those with removable presta cores!