Lasers for hair removal, at least the ones around now, work by targeting the brown color in the base of the hair follicle and hair bulb. This target selectively absorbs the laser energy, and heats up so much that it damages the follicle so hair won't grow well anymore.
Red hair is hair that has a lack of brown pigment, biologically. This really does mean it can't offer itself as a good target for these lasers, unfortunately. There may be lasers developed in the future that use a different target, but it's hard to imagine right now how that technology will be created.
In the meantime, electrolysis works differently, by using an electrical current to directly damage each follicle one by one, and isn't hindered by the color of the hairs. This is why it works for blonde or gray hairs, too.