You haven't been to many weddings. Mullahs don't show up if the thing is no segregated. This just happened last week.
There are many Mullah who do not care to impose segregation so one should look for those kind of Mullahs , also people think that Mullah is needed for Nikah , no he is not . Anybody can get the form for Nikah fill it and get the nikha registered.
The following is the minimum requirement in Sunni sect:
Nikah is performed with a proposal (Iejaab) by the male or female and acceptance (Qubool) by the male or female in the past tense and in the presence of two male Muslim witnesses.
It is Sunnat that the marriage be announced and performed in the Masjid and the bride be represented by her Mahram (Unmarriageable relative like father, brother, etc.). The bride gives consent to her representative (Wakeel) in the presence of two witnesses to perform her marriage at the Masjid. At the Masjid, the Wakeel represents the bride in the presence of the two witnesses and the stipulated dowry. The witnesses must be two trustworthy and pious male Muslims who are not her ascendants e.g. father, grandfather or descendants e.g. son, grandson, etc.
The Mahr is the woman's right and should be stipulated prior to the marriage.