catalysts have no effect on the equilibrium constant.why?

A catalyst is a thing (atom, molecule, element.. etc) that speeds up a chemical reaction by lowering the activation energy(Ea) without being altered itself.so, it only cause the reaction to occur faster, but will not have any affect on the equilibrium constant (which is concentration of products to the concentrations of reactants).. also, since catalyst is not altered, it should come out as it went in. activation energy (Ea) is the energy needed for a reaction to initiate.both reaction such as endothermic or exothermic has Ea,so we need to overcome the Ea for that rxn to proceed.it absorbs the reactant particle on its surface reducing their bond energy.when the energy between the bonds is weaker,,its easier for the reactant particles to change to products.Ea comes from when reactant particles collide with each other with high kinetic energy. some substance are called catalysts but do actuallly get involved in the reactions.they are not true catalysts because they are reacted out in the reactions,.these pseudo catalysts could drive a reversible rxn further towards completion and could appear to alter the equilibrium constant.