Have you ever tried measuring ionic analytes or organic acids with High-Performance Liquid Chromatography (HPLC)? Good luck with that!
The scope of HPLC is very limited for analyses of standard anions, cations, organic acids, and sugars in water and various foods, for example. For such analyses, ion chromatography (IC) is the better solution.
Why? IC can separate multiple ions and detect them using a conductivity detector. And because chemical suppression lowers background conductivity, sensitivity is not an issue, making IC suitable for trace- and ultratrace-level measurements.