Why are concentrations of ion in water analysis quoted in ppm

thanks!

Because of math anxiety. When dealing with small quantities, we invent new units for measurement. That gets rid the decimal points, 0.000032 g, or negative powers of 10. A value of 3.5 ppm sounds good. If its 0.0035 ppm, what do you , call it 3.5 ppb. Also its is easier to compare values like: 0.0000056 and 0.0000021 by using 5.6 ppm and 2.1 ppm