Few males achieve any real freedom in their sexual relations even with their wives. Few males realize how badly inhibited they are on these matters. (Alfred Kinsey)
Kinsey did not cite 3, 4 or 5. Many men go to prostitutes to get fellatio, which their partners refuse to offer. Mostly it is younger men who go, sometimes just to experience what it feels like. Men also go to get sexual interaction that wives would not supply including fetish type activity. Foremost men go to prostitutes because it is cheaper than any relationship with another woman and they are not obliged to offer the romantic interaction that women tend to require.