Why not just use clear bottles to store chemicals as long as they are stored in a dark area?
The specification for "brown bottles" applies to glass bottles only and has absolutely nothing to do with blocking light from striking the chemicals.
Glass, when made purely from silicon, is far from clear. To make it clear, other chemicals are added to create a blend. Some of the added chemicals, particularily lead (think, lead crystal -- lead is what makes the glass beautifully clear) can leach out and affect the chemicals. Medicines and lab chemicals are best stored in non-reactive glasses. Such glass is naturally an ugly hue so additional brown dye, safely inert, is added to make a uniform brown.
Plastic bottles don't need the brown, but tradition is what tradition is. Most plastics do absorb some of the chemicals they store so you should never use a bottle that has ever contained anything that would, in trace form, harm the chemicals you put into them. A used household bleach or vinegar bottle will destroy developers but is reasonably safe, if well washed, for storing stop baths or fixers (both being acidic and vinegar actually being the most common chemical for stop, albeit is a more concentrated form, and a common component of some fixers).
Most plastics also breath. Thin disposable PE bottles used for bottled water and such often breath too much to safely store developers and other chemicals that age rapidly when exposed to oxygen. The bottle sold for photo chemicals generally have thick walls.