When you smell the chlorine it is used up. You add fresh chlorine to get rid of that residue(shocking). It’s a fairly complex chemistry balance for a homeowner so they often get it wrong. Even salt pools extract chlorine from salt.
Bingo. What you are smelling are the chloramines.
The exception being if the pool has just been charged with gas chlorine and there is residual gaseous chlorine lingering, but that dissipates quickly.