Alrighty, so, going to go on a little tirade about my thoughts on marriage in real life before giving my opinions on whether it should be included in the game.
In real life I am vehemently against it. I think it's an artificial social construct. I do not believe it is inherently an expression of love, I do not believe it strengthens commitment. At best I find the whole thing to be a pointless waste of money and at worst I find it to be a lie people tell themselves will fix a relationship that is beyond repair. I take that back; at worst it's a sale of property, but that is rarely the case in the western world these days.
I personally believe that if two people love each other, want to be with each other, want to stay with each other for the rest of their lives, then that is all they need. That mutual desire, respect, and commitment between them. I don't think there is any reason to put on a song and dance, make a circus out of it, and have their love declared by a religious authority, justice of the peace, or captain of a ship. The decision to commit to one another is between the two people making that commitment and no one else, and a metal ring with an overpriced rock on it isn't going to make that commitment any stronger.
If two people want to get married, that's fine, that's their choice. I just don't see the need for it, and it certainly isn't for me.
Now, as to whether or not it should be included in the game.
Personally I would not have a problem with the option, and I stress, option of marriage being available so long as Andromeda's plot takes place on a reasonable time scale for it. Certainly a longer period of time than any of the previous games individually covered.
I can see where you're coming from, because I've seen some of the same things. So I'm not disputing that your ideas are valid. You have some good points. 
However, as someone that is legally married and has been for years (just hit 9 years married and 11 years with the same person,) I would like to speak up.
I know what you mean, but that really doesn't apply to everyone. We didn't get married because we felt I had to. We wanted to. We wanted to stand up before our friends and family and declare our love for each other. It wasn't a stupid song and dance for us. It also wasn't like I dragged my husband kicking and screaming into a ceremony. He proposed to me, and was helping me set the date for 20 months after we got engaged. We wanted to see if we could live with each other and get along first.
We had talked and planned for it. We got married at the Renaissance Festival, so folks could go out and have fun that didn't involve us once the ceremony was done. It was also a chance to see friends and family that we normally don't get to, since many of them live a state or more away. We didn't spend a lot of money either. It wasn't a circus. Well, the best man locked his knees during the ceremony and fainted in the middle of it, so I guess we had some accidental acrobatics. Ours was under 40 people, and most of those were my husband's extended family. I have a small gold band around my finger, and so does he. I never owned a "rock" in my life, except for the wedding band I inherited from my grandmother. That I never wear. We did all these things not because we were forced to by anyone, or obligated. We did all of those things because we wanted to.
You're right, it didn't save our relationship, since our relationship was fine. It didn't strengthen our relationship, time and later experiences did, and I've seen folks married and divorced who thought that marriage would save their relationship. Like my best friend of 18 years. He thought marriage would save his relationship. He was wrong.
My own brother and his wife aren't legally married, and have no current plans to do so unless their daughter starts asking them to when she gets older (she's almost 2.) They still have separate last names, and are very happy together. They've been together for over 15 years now. My parents had a tiny wedding (like 6 people) because their mothers insisted on it. They just hit 36 years of marriage and 38 years together. What can work for one couple may not for the other.
I personally think of someone wants to get married and do the formal ceremony, then they should. If they don't want to, then no one should tell them they have to.
As far as the topic goes, I agree with Iakus. I think it would be a fine option for some romances. Using DA:I as an example, I could see Cullen as wanting marriage. Iron Bull does not, and prefers the current arrangement of comfortable monogamy without marriage.