Because Las Vegas, in general, is a favorite destination year-round by all (kids and adults alike, gay and bi and straight, married and not, etc.), Las Vegas hotels have made it their priority to offer more aside from the lodgings business. Some of these hotels offer shows, fountains, light shows, plays, concerts and amusement centers (or free/discount tickets to these) with their welcome drinks and complimentary breakfasts. Some even offer free transportation.
Just do your research and compare prices. Do not be easily enticed by so much freebies since they might not be ones you really need or want. If you're honeymooning, ask for honeymooners' incentives like a better suite, free champagne, or seats in a show.