Women's demands and expectations have skyrocketed.
Guys know they can't meet those,are scapegoated for almost everything daily in popular culture,and for decades women have been telling us they are strong/independent/don't need a man.

So you can't blame guys for giving up, when 50% of the guys they know will be divorced. it's easier, more fun,and more interesting and rewarding to go travelling, buy a motorcycle, hang out with friends etc than to be beholden to a girlfriend or wife.

When you gave the wrong impression of yourself.

Sir Lancelot didn't show up with flowers for Queen Guinevere. He just rode in on his noble steed, armed with only his charming wit, maybe a few rehearsed lines of sloppy lust filled poetry, and his enormous protruding sword of deflowering virtue to win her over.

It happened when (some or most) women accepted this as okay behavior. If women had higher expectations as to what it should take to date them or sleep with them, men would strive to meet those expectations.

It became overrated apparently.

Yea girls never do that.... lol

Cost money whereas a call doesn't

Funny story:
Got a some off-white roses at the store on Thursday. The last bouquet was starting to wilt, and I was getting food anyway.
Gave it to my SO. This happens a lot, just because. Also, winters suck. And I like to support the Colombian economy. Cut flowers better than coca leaf.
She was going to hang out with her mom. Suggested she pass them along, if that would please her. She gets flowers from me fairly often.
So her mom got the bouquet... And cried. Because that never happens for her, and she couldn't remember the last time.
Win.

To answer your question, romantic people are not obvious. You can sometimes tell by observing their manners in social situations. But that insight seldom happens anymore, because Technology And Social Media Are So Much Better.
Also, these silly, sentimental fools are most often already in relationships. They're good at it. Rarely found in the wild. Their partners prefer to lock it down.
Mine ordered custom, exotic-alloy engagement rings from Europe. Serious business.

I'm thinking about the same time that women decided the only time they should approach a man would be for sex and they would make it clear that any sort of relationship / friendship is off the table. Quid pro quo.

they want to screw you, not date you.