It makes me wonder if the upcoming product involving feywild stuff might have new rules and/or features for PCs gaining or starting with lycanthropy and they are worried about balance issues (especially for PCs at low level)? As we've seen with barbarians while raging, halving their damage can get kind of irritating for a DM after a while because you just have to really pound on them to truly affect them. But now imagine having a party of like 3 barbarians and a couple other PCs? You'd have to overload the battlefield to put enough firepower on there to hurt the barbarians, but you also are running the risk of wiping the other PCs at the same time because they can't take the same sort of heat. That's kind of like what would happen if you had a party where half the PCs had lycanthropy.
At least with Regeneration, that just gives you a small handful of healed HP at the top of each of your turns. Healing say 5 HP at the start of your turn has much less impact on the game's balance than halving the damage on each and every attack you take in a round. Resistance could save yourself from 10, 20, 40 points of damage a round... Regen would only get you back a handful.
Personally whatever the reasons are they won't really affect me, because to me lycanthropy has really been neutered as a concept with the proliferation of Wildshape. Druids don't drop all their clothes and equipment when they turn into animals like weres do, and they essentially have two pools of hit points (their humanoid and their animal forms) to just absorb so much damage (where lycans have one pool and only get Resistance up until the PCs gain magic weapons-- which happens probably at like level 5). A PC who is cursed with lycanthopy to me is just a poor man's Wildshaper. It's not deadly or a problem, it's just annoying.