Why is "idle speech" one of the ten unwholesome actions? According to the Suttas, "idle speech" is one of the ten unwholesome actions which generate bad karma. I understand why the other nine unwholesome actions would generate bad karma, but I have a lot of questions about the Buddha's claim that idle speech does the same. 

First, let's take a look at some relevant suttas to determine what the Buddha meant by "idle speech". An oft-quoted passage, found in DN 2, suggests that practitioners should only talk about dharma-related topics and nothing else:


  Whereas some brahmans and contemplatives, living off food given in faith, are addicted to talking about lowly topics such as these — talking about kings, robbers, ministers of state; armies, alarms, and battles; food and drink; clothing, furniture, garlands, and scents; relatives; vehicles; villages, towns, cities, the countryside; women and heroes; the gossip of the street and the well; tales of the dead; tales of diversity [philosophical discussions of the past and future], the creation of the world and of the sea, and talk of whether things exist or not — he abstains from talking about lowly topics such as these. This, too, is part of his virtue.


This passage, however, describes the behavior expected from buddhist monastics, not ordinary lay buddhists. So where do the suttas talk about idle speech for laypeople? One example is MN 41, in which the Buddha explains to a group of laypeople which actions lead to bad rebirths. About idle speech, the Buddha tells his audience the following:


  He engages in idle chatter. He speaks out of season, speaks what isn't factual, what isn't in accordance with the goal, the Dhamma, &amp; the Vinaya, words that are not worth treasuring.


The words "what isn't in accordance with the goal, the Dhamma, &amp; the Vinaya" seem to imply that just like monastics, lay followers should restrict their speech to topics related to the practice of buddhism. I have two issues with this idea.

First, it's impractical. Laypeople lead social lives, and in DN 31 the Buddha himself talks about the importance of good friendships. It would be practically impossible to establish and reinforce social bonds without engaging in any conversations about worldly topics.

Second, the reasons buddhist teachers usually give for avoiding idle speech are practical rather than moral. Teachers generally tell their followers that by engaging in idle speech, they are wasting their time and distracting themselves from the study and practice of the dharma. While these are undoubtedly good reasons to cut down on idle speech, it doesn't explain why idle speech creates bad karma. If distracting yourself from studying and practicing the dharma creates bad karma, why aren't other distracting activities included in the Buddha's list of unwholesome actions? Engaging in idle speech isn't inherently more distracting than other leisure activities, such as consuming entertainment (i'm aware that in DN 31, the Buddha discouraged his lay followers from attending public spectacles. However, the reason given for this rule is that frequenting public spectacles has negative consequences in this life, not that it generates bad karma).

So how should I interpret the Buddha's teachings on idle speech for lay followers? I'd like to hear what prominent teachers have to say about this topic, but everyone's perspective will be appreciated as long as it's well substantiated.

Thanks in advance for your answers!
So how should I interpret the Buddha's teachings on idle speech for lay followers? 

Opening pleasantries are not idle talk; they frame a discussion by providing social context:


  He went by carriage as far as the terrain allowed, then descended and approached the Buddha on foot, and exchanged greetings with him. --DN16


And neither is talking about suffering, its origin, its escape and the path to escape.


  “Mendicants, do you remember the four noble truths that I taught?"


Have you noticed that although people may idly brag about their wealth, good family and good fortune, what they often really wish to talk about is their...suffering? Indeed, there seems to be a high correlation between idle talk and suffering.

Therefore, from a practical point of view, I've found that we can all talk about our own suffering and its escape. Such talk is not idle and often leads to friendships and trust. 

In terms of movies and shows as idle talk, even these are opportunities to discuss suffering. Movies and shows are all about suffering. 

So when someone approaches with idle talk, gently listen and ask them about their suffering. Then listen and speak with an open heart. Become a quiet person known as a good listener and a good friend.


  Good friends, companions, and associates are the whole of the spiritual life. --SN3.18