Regular sex and for pleasure is a new concept. Modern contraceptives didn't always exist, and in the past, sexual intercourse almost always ended in pregnancy unless you were smart.
It's not my place to judge how many sexual partners someone has, or whether I think 5 is enough, 10, 50 etc.
In all honesty, is a girl having sex with her boyfriend 200 times in a year better or worse than a girl who had sex only 4 times, but they were all one night stands? What makes the one night stand so much different? Because it was different guys?
People need to just be smart. There is reason STD's are an epidemic now, where 1 in 4 has herpes, and 1 in 5 will contract an STI at some point in their adult life.