I do believe LimbSavers and other recoil pads have a legitimate purpose.
I'm a big proponent of their use for new shooters. If no instruction is available, a recoil pad can help compensate for a lack of technique while a new shooter learns the weapon mechanics. How many folks actually take shooting classes/lessons vs. simply just picking things up on their own, from friends, or from sites like ours? Without a decent recoil pad, a new shooter's first experience with a 12 gauge can be quite unpleasant and in some cases enough to make them not want to shoot it again. I look at a pad as effective as a LimbSaver as sort of "training wheels" for shotguns. Many are simply intimidated by shotgun recoil. Aside from mitigating recoil a cushy pad can be a valuable tool in helping to reduce a new shooter's fear/anxiety which can be their most difficult obstacle. Once a shooter's comfort level and confidence with the weapon improves, establishing proper technique becomes a lot easier.
Other subsets of shooters might not shoot enough to practice proper technique, or even with practice still find that they need the extra padding. Everyone's comfort level is different and what works well for some doesn't always work for all...