For me and honestly saying i prefer the woman that hide her attraction from the strangers,
but that is my opinion which may differ from the others.
While I understand where you're coming from, I think this needs to be put into perspective a little bit:
a) are not showing their 'attraction' to strangers, they're getting a tan
b) they're on a beach - too much clothing makes things awkward
c) it's a different location from ordinary life with different context and values on modesty. Wearing a bikini is not immodest on a beach in most Western cultures; in fact, in many places, going topless or even nude isn't immodest. Context is very, very important.
d) it's a different country
e) most people will not regard them as showing their 'attraction'. They're not getting their boobs out for people's enjoyment.
and of course, the most important one:
f) it's their choice whether they want to wear or reveal: I've seen people on beaches wearing more conservative clothing that haven't gone to great extremes.