Well it depends on what you mean by marital love, I assume when you say mean marital love by people who loved their spouses? Well, this has been happening for quite some time. It is not a modern notion, and married couples of the past did love one another. There are examples such as Henry VII of England and Elizabeth of York. Henry VII was one of the few faithful Kings in a time where it was expected for Kings to have a mistress, and though the marriage was a political one, the two did eventually fall in love with one another. And when Elizabeth died, it caused Henry to mourn deeply for her. His son, Henry VIII of England, so many times married for love (and of course for a male heir), and indeed I believed he loved some of his wives like Katherine of Aragon and she definitely fell in love with him. Suleiman the Magnificent loved Hurrem Sultan so much that he freed her and made her his legal wife. Louis XIV fell in love with his second wife and married her (though the marriage was kept secret and not addressed due to the difference in station between the two). As from the examples, even in environments of politics and royalty, people still fell in love because undoubtedly it is apart of human nature.
Now I think an important part of this question is how often did people marry for love? Amongst royalty and nobility throughout history (with some exceptions) most people married to secure political alliances and their families fortunes. That is why Kings married more often than not foreign princesses. The good of the individual was second to the good the country or family. Now of course, people defied this, and the results varied. Edward IV of England married Elizabeth Woodville, and it was outrageous for the time period, as the nobles and people of England expected him to make a grand match with a foreign princess. Mary Boleyn married in secret her second husband and thus was banished from court by her family (though Anne Boleyn seems to have softened a bit and sent her sister gifts). And as mentioned, Henry VIII caused great scandal when he annulled his marriage to Katherine of Aragon (daughter of two monarchs, and of great lineage) to marry Anne Boleyn, a woman of no great lineage, indeed Henry had to bastardize the coat of arms for Anne Boleyn, to make her look more worthy as a Queen consort. As for the peasant and middle classes, I would suspect that marrying for love was a bit more common amongst them.
Sources: general knowledge of history The Winter King by Thomas Penn several books on Henry VIII and his wives.
The answer is difficult. Although there are textual references to marital love since Antiquity, we do not know if their concept of marital love corresponds to ours.
Often, marital love often appears to have been a bonus, or a relationship goal, not a priority or a requirement for marriage.
Late-medieval and early-modern authors actively advocate marital love. Erasmus and Milton are often cited examples, though the theme of marital love appears in medieval sermons, and is quite present in the literature and visual arts of the Renaissance throughout Europe.
Sources:
James, Learned Girls and Male Persuasion
Rummel, Erasmus on Women
Crawford, The Sexual Culture of the French Renaissance
McCarthy, Marriage in Medieval England