Tablets are a poor form of supplementing. They are called "bed pan bullets" by hospital nurses for a reason. You are literally crapping your money and health down the toilet when they pass right through you. Look at the ingredients list on any supplement label - should you really be consuming all of the fillers, binders, flavors, coatings, etc that they use to form tablet pills? It is a health product right? Maybe it's better that your body NOT absorb all that junk they put in tablets.
Capsules are better but they too usually have added fillers and binders etc and are still more expensive than powdered supplements.
In my opinion the best (and usually least expensive) form of supplementation is 100% PURE powdered form, such as vitamin C powder. Pure powder is pure product and thus more dense, is absorbed better, can be mixed in liquid of your choice and with other powders, and is usually more cost effective than pills or capsules. Some companies add magnesium stearate etc to powder so you still want to look at the labels on anything you buy and make sure it only has one ingredient on the label, such as "Ascorbic Acid" or "Calcium Ascorbate" etc...