Why is reduction mostly associated with proving hardness? Reduction is a powerful problem solving technique that is helpful in solving problems in terms of the solution to other problems, it can also be used for complexity analysis. Why does most of the literature restrict mentioning reduction to proving hardness which seems to be a pessimistic point of view for reduction (unless P=NP ofcourse :) )?

EDIT: Just to make sure my question is well understood. I am aware that reduction is used for problem solving and designing or analyzing algorithms, I have solved hundreds of contest problems with reduction which leads to my question of why is a random search for reduction lead to the NP completeness context with book chapters and papers illustrating its power from the complexity theory point of view when the same basic definition for reduction can be used for designing algorithms but just rarely (or implicitly) mentioned. In other words, why does a random sampling of the occurrences of the term "reduction" show a clear bias towards its use in complexity theory.
Actually, people do commonly use reductions for both purposes: both for proving lower bounds, and for designing algorithms to handle a certain problem.

For instance, it's very common to reduce a problem to linear programming, to a max-flow problem, or to another well-studied problem.  This is using reductions for solving problems.

Any particular textbook might focus more one or the other use of reductions.  That's a philosophical choice on the part of the author.