I don't particularly believe in supping with calcium.
Modern day agricultural practices have depleted our soils of calcium .supplementing calcium unfortunately is one of the few ways to to replenish our calcium deficient bodies.
Ascorbic acid has a pH of 2.2 and calcium needs an acid to become absorbable, so something like calcium ascorbate is the ideal way to neutralize the acidity of ascorbic acid and make calcium available to the body!