I'm talking about the kitchen sink. Why not just connect the filters to the regular tap?
The kitchen sink is used for various other purposes than getting a glass of water to drink. So you don't want to be wasting the filter when doing your dishes.
This contact time requirement restricts flow significantly, so much that you would not be able to efficiently perform other common tasks that are normally done in the kitchen sink: rinse/wash dishes, wash fruits and veggies, fill pots with water, wash hands, etc.