Since the Lord God himself is the temple of the city (= bride, church), it is pressing that those who belong to the church speak of the church as holy, something divine. The church is not a social club where friends and/or like-minded people perform a specific liturgy. A church is where God is present, and so demands a holy attitude, God-pleasing demeanour, activity, dress code, etc.
22 Je ne vis point de temple dans la ville; car le Seigneur Dieu tout-puissant est son temple, ainsi que l'Agneau.