The Puritans forbade a large number of entertainments, some of which modern Americans (even Christian Americans) do not believe are problematic. Dancing, gambling, and theatrical productions were forbidden, as were celebrating most religious holidays (even Christmas!). Although drinking was legal, drunkenness was a crime, and though smoking was legal, it must be done in private.
The reason for these strict laws was that the Puritans believed one of the purposes of civil government was to help citizens live pious lives. They wanted their society to be a "city on a hill," and that required the limitation of immorality. At best, frivolous entertainments would distract people from Christ and their occupations; at best, they would result in the damnation of their souls. As Puritan theologian Richard Baxter explained in regard to theatrical productions:
I cannot but look upon all the glory and dignity of this world, lands and lordships, crowns and kingdoms, even as on some brain-sick, beggarly fellow, that borrows fine clothes, and plays, the part of a king or lord for an hour on a stage, and then comes down, and the sport is ended, and they are beggars again.
He believed that the theater distracted people from their true situation in life and was thus harmful to the "city on a hill" the Puritans were trying to create.