There has to be a balance of both to be happy long-term.
If you're not "in love" with someone eventually it will show in how you behave with them. People who want the kind of love that (they) themselves are unwilling to give are essentially selfish cowards.
Most likely they had their heart broken and promised never to allow themselves to be as "vulnerable" again or be "all in" with anyone.
It takes more (courage) to fall "in love" a second or third time than it does the very first time. With each breakup we carry some baggage.
Oftentimes we enter into a new relationship without detoxing our past.
A person who is NOT "in love" is far more likely to cheat, be abusive, or inconsiderate of one's feelings. They can "take you or leave you".
"Never love anyone who treats you like you're ordinary."
- Oscar Wilde
However if (you) are not "in love" with your mate odds are you'll be fantasizing about being with someone who really does melt your heart or excite you! There's a good chance you'd consider cheating.
People cheat in order to stay in or tolerate unhappy marriages.
Not being "in love" with your spouse is ultimate definition of "settling"!
The world may not owe you anything but you owe yourself the world!
One man's opinion!:)