...And fun starts. Amount of views and contribution of newcomers from other sites / tags much increases, along with the risk of things getting out of control.
You know, everyone would want to answer a question, but for community regulars, this natural desire is balanced by established norms. Regulars understand what kind answers are good and likely to bring upvotes and they avoid posting garbage that usually gets downvoted: this sort of sets the quality norm.
But wait, the question is now on top, it attracts a lot of visitors whose desire to answer is not balanced by local community norms…