There is a Gemara in Kiddushin 12b where Rav says:
d'Rav Mangid Al d'Mekadesh b'Shuka
Rashi comments: Mishum Peritzusa
Rav would flog anyone who does kiddushin in the shuk because lfi Rash it's pritzus. So then why nowadays do kiddushin under the chuppa in front of everybody? Also, why is chuppa/nisuin l'chatchila done in public? How is it different than kiddushin?
Menachem Zaman, Sherman Oaks
Very nice question! Perhaps one could understand that the Pritzus of performing marriage in the Shuk is when it's done in a casual and informal manner, without the sanctity and sincere modesty of a customary Chasunah. When, on the other hand, it is done in the context of a formal wedding ceremony , even if there are many people there, people do treat it with more respect and Tzeniyus. This would avoid the problem of Pritzus that Rashi explains is involved when it is done in the Shuk, since there people would be prone to gawk and not accord the proper dignity and privacy to the Chasan and Kallah.
Best wishes,
Yishai Rasowsky