Here is my take from the female view point. Women grew up watching the Love Boat on tv and some still secretly hope to meet Mr. Right on a boat not Mr. Right Now, which is who they usually meet instead. Women are romantic, and we enjoy men in uniform also, (the staff). Men don't want to room with a strange man (homophobes this means you!) women are more willing to take that chance. Crusing provides good service, pampering spa services, shopping, sight seeing, dancing, music and shows, most women enjoy this stuff so do some men, did I mention shopping.
Guys like cheap drinks, sports etc... Not all but most. Guys don't think wow lets go on a cruise, they think lets go to Vegas and hit the casino and strip clubs.
Guys spread the word to each other this is a great way to travel and maybe meet a lady or two. If no romance I still think you will have a good time, and at least make friends, but go with an open mind and no expectations. If you want instant gratification for a cheaper price tag go to a strip club like Ferret says