Incentives. I witnessed the game change completely from people having as their main objectives things like harvesting materials, building a shelter, hunting for meat, scavenging POI's, and starting a garden-- and doing those things in an organic and survival focused manner to the game becoming all about chasing experience points for the purpose of leveling up as quickly as possible.
Now I'm not knocking that type of gameplay for those who like it but it was a dramatic departure of the types of incentives and rewards the player was exposed to and in my opinion-- not for the better.
Even the new system (imo) gives too much incentive to the player to directly increase their experience and level up by grinding even without LBD acting as highly addictive drug for that gameplay style. I have just one last hurdle to overcome which I'm hoping to get help on this week and then my mod will be ready for public testing in which xp is completely bypassed. You will gain skillpoints simply for surviving for a full day and for completing quests. Whether you kill zombies, avoid them, mine, farm, scavenge, trade...whatever—None of that will gain you xp and no activity will act as a missed opportunity where you could have done something else more valuable to level yourself up. You will take actions for their own merit and not as a means to gaining xp efficiently.