If you need to depend on your relatives to survive, then it could very well be risky to choose marriage partners based on romantic love. This could work if the families got along with eachother, helped support eachother etc. but if they were enemies or disliked one another on some level, it could cause a lot of problems between the spouse and their own families or the way of surivial for the families in general.

I don't think that marriage is the only way to successfully have a relationship or raise a child. It all depends on the level of commitment and trust you have with someone and if you both agree to either get married or not get married. This might be challening in certain situations because of some feelings towards having children out of wedlock. It could present problems with family or religious institutions and may be harder to be accepted in certain societies. Although in others, it may not be looked at very carefully at all and simply seen as normal or completely acceptable.