The chemical reactions of life are subtle and complex. Let us look at the conditions necessary for complex chemical reactions to occur. In solids the molecules are held together in fixed positions relative to each other. In gases the molecules are flying around free of each other. Reactions in liquids, however, can be controlled by things like concentration, acidity, and temperature.
Liquids provide an excellent medium for complex and subtle chemical reactions.
In fact it is difficult to see how the complex reactions of life can occur in anything other than a liquid medium. Unfortunately, the liquid state is the rarest in the Universe. Liquids are always 'leaking'. In the vacuum of space there is nothing to hold a liquid together. A drop of liquid would quickly evaporate.