I'm reading the primary source of St. Benedict's rules for monastery life. It exemplifies a lot of cliches about Christian piety--that they don't allow laughter, talking, sex (obviously), or really anything happy at all.
What made them this way? Because I can't imagine that anyone would work so hard to avoid happiness unless they had a really good reason. And lest you say that the reason is heaven, it still begs the question why heaven was so important to them; we don't usually idealize that much unless our lives are unbearable.
Maybe the fact that Rome (a symbol of decadence), which had been the leader of the known world, was sacked around that time (532 CE) and led people to see worldly-indulgence as bad?
If this doesn't qualify for top-level comment, please remove.
What we have to remember is that the rule was written for monks, not lay people. Even today, we have monasteries that forbid speaking totally (Carthusians e.g.) as well as other monasteries still inspired by the rule of St. Benedict.
The path of monasticism follows that of asceticism, which is simply a radical renunciation of life for the sake of God. They understood, even as they understand now, that life has so many distractions that prevent them from loving God in himself. This is exacerbated more by their understanding of human nature as fallen nature, one where human passions easily exceed the ordinate amount due to created things (food, leisure, etc.). So the means were to control and subdue human passions, hence asceticism.
Asceticism itself arose simply as a response to a denial of their own life, which was required of Christians. "Whoever wants to follow me must deny himself and carry his cross". This words of Jesus pretty much became the basis of 'denying one's self'. Earlier on, martyrdom (even if the exact extant of it was probably less than in the popular imagination at that time) provided a concrete means to 'deny their life' and offered it to God. It was the model life of a christian. But after the Edict of Milan, martyrdom can no longer be an aspiration for 'giving up one's self to Christ', hence the so-called 'white martyrdom'.
In the East this developed into hermitage, where individuals would flee to deserts and fast as means of achieving holiness. The sack of Rome hardly invented asceticism, as Eastern hermits in the 4th century were already thriving after the inspiration of Anthony the Great, the pioneer of Eastern hermitage.
In the West they formed communities. The rule of St. Benedict pretty much exemplified the theology of the time. Today, it is understood a bit differently. Although asceticism is still a valid practice in monasteries and everywhere else, it is also realized that one can deny one's self in various other ways that do not necessarily impose violence on one's self.
Restriction of natural tendencies allows control. If there are no rules to abide to then there would be no hierarchical control possible. There would be no reason to punish someone.
Abiding to the rules allows to signal dedication and obedience to the common cause, which is a very useful promotion tool for an organisation such as a monastery.
Promoting only the people that abide to the rules causes a positive feedback model in which rules will get more restrictive and restrictive until they are almost impossible to follow.
