We use an alcoholic medium for reactions in which we want to prevent the characteristics of the anionic species and an aqueous medium for the reactions in which we want to control the activity of the anionic species (depends on how strong is our solvent).
The principle behind this is that alcohol solvates the cationic species only while water in an aqueous medium solvates both cationic as well as anionic species. The solvation results in neutralizing and reducing the mobility of the solvate and thus reduces the reactivity proportional to the degree of solvation.
Now back to my question Why does alcohol only solvate the cationic species despite being a polar protic solvent just like $\ce{H2O}$?