Entering the Nirvanic precincts, the sacred state of samadhi, experiencing that incomparable bliss, is the goal of any spiritual practice. And obviously this isn't the kind of goal the serious practitioner would even want to attempt in a public environment. Prayer and meditation are personal and private endeavors. Every Zen Buddhist knows this as well as every Christian. When you succeed in meditation, it shows.
Fellowship can be valuable.
Human nature is such that people often need the feeling of security that comes with belonging to a group. And so we find many Zen organizations whose members regularly meet in order to sit on their cushions and then to enjoy a cup of tea and some spirited conversation afterwards. Jesus didn't say that you shouldn't go to the Temple. He said that when you want to communicate with God, don't make a public spectacle of your piety. Talk to God in private.