Me and my wife haven't been to a beach in the last 15 years, usually go into the mountains. So I no longer have any insight into how the relationships, topless or not, are nowadays.
My wife was already a lover of topless sunbathing before we started dating. I had been able to experience this myself a few times because we used to see each other regularly through common friends. This was usually on a waterfront where we went jet skiing. The girls then usually retreated to a quieter place to work on their tan, most of them topless. My girlfriend at the time dared to wear thong bottoms. Needless to say, the guys stopped by the girls once in a while.
After we started dating and had sex the first time I saw that she also had a thong tan-line
, apparently she never dared to wear them there at the waterfront.
These days, she still takes every opportunity to sunbathe topless when we're at a hotel pool. Often her example is quickly followed by other guests. You can see that most women don't like to be the first and use some encouragement.