So I've seen this advice quite a lot in this sub, but I fail to understand how it's a good idea.

So there are two versions of this:

1) Moving in after getting engaged, with a wedding date being set:

Isn't this incredibly irresponsible? You are engaged to be married to a man, who has only shown you the best side of himself and you have absolutely no idea how it is to live with him and share a household with him.

Wouldn't having a wedding date picked out, all your friends/family expecting a wedding and possibly having deposit given to the venue/photographer/etc. discourage women of breaking up, if they realise while living together, that the man is not that great after all? Wouldn't all those things pressure the woman to go through with the decision they made while not having all the information needed?

2) Moving in after getting engaged, without a date being set:

So you have said yes to a man that you are not yet sure if you want to marry. I definitely think this version is better than Version 1, but how is this different than being a live-in girlfriend? To me, it sounds like only the name of it is different, but everything else is the same, including the chances of you two eventually getting married.

What am I missing here? Shouldn't "marrying a good man that fits you" come before "marrying a man, who wants to marry you"?