I am with dageir with this, I agree with all of his points.
H&H is buggy as hell, those bugs have become so engrained it would probably become much harder if they were fixed and less enjoyable to most people. the tanning bug, the cooking bug (and more that I have yet to exploit) make the game very very simple mechanics wise. The grind is lessend by the fact you can just pile your oven full and then add 1 branch to cook everything perfectly, rather than the intended different timed cooking recipes. Leather tanning takes a matter of minutes rather than hours, means building that palisade is reduced to minimal time investment.
Are the simplifying bugs in Haven the reason for its popularity? Probably not but they help.. I really enjoy the fact that a starter player can do the same amount of work as a seasoned player, I can do stuff without having to eat every 5 seconds. I really enjoy the fact that LP's can be earned extremely easily all the time andeven when offline and LP's are the lifeblood of the game. I enjoy the fact there is a pretty clear scaling of difficulty from farming to produce better crops and hunting from foxes to bears. Alts are reidiculously easy to make and starting up from a loss is childsplay.
Salem.. is monetized.. Silver is the life blood and if you cant play a lot you cant make a lot.. and if you cant make a lot.. things slow... right ... down. Dallane said it becomes easy to get once you can hunt argopelters.. but probably hasnt tried to level an unassisted character up in the last 6 months.. its slow.. it gets slower and you need to invest massive amounts of time to get rewards which are very shortlived.. I cant plant and farm 200 fields with my current play style.. So I cant get the hay needed to fast tier my fields.. I cant generate the amount of coal needed for speedy crops.. All fo that takes more time than i realisicly have available..
H&H is so much more forgiving on a time table and I feel this is a massive attraction.