There is also a saying that goes: "The person with the least amount of interest in the relationship (controls) it."
Personally speaking I don't think I could spend the rest of my life with someone I did not love simply because they were "in love" with me and would do anything I asked. This reminds me of a hit song from the 1960s by Jimmy Soul that stated: "If you want to happy for the rest of your life never make a pretty girl your wife."
The implication is an ugly woman would be(grateful), try harder, love, and appreciate her man while a beautiful one would be demanding and forever draw out competitors. Odds are if you don't love the person you are with you are far my likely to be open to cheating on them. In my opinion the definition of a soul-mate is when both people share the same values, want the same things for the relationship, agree on how to get those things, and (mutually) feel the same depth of love for one another.
There's nothing wrong with causal dating or even (friends with benefits) for that matter but if one has decided to be (in) a relationship or get married then they may as well be (all in) and shoot for the moon! I'd rather be in a situation where both me and my mate are crazy in love with one another. - One man's opinion! :-)