I know this one is hard to sell to some, but I really like the mattress on the floor look - and not just the look, I like the idea of it, as well. Do we really need furniture holding our mattresses? Beds are a pain to move/put together, they squeak and groan, they might damage your floor, and usually the support of a solid floor will make a mattress feel a lot more comfortable.
Historically raised beds offered some protection from various critters, (they still might in wilder parts,) and some people with mobility issues find it easier to get in and out of raised beds, but most of us are not in either category.
Mattress on the floor seems to be an identity/status issue for most of the people I talked to. They usually don't have substantial arguments against it but often say things such as "it's the dorm room look" or "it's like you can't afford a bed." Clearly, it's not for the conformist but to me a mattress on the floor says "I am fit enough, I live in a critter free home, and I have better things to worry about." I am not promoting some monk-like, bare-essentials type lifestyle here. Simplify your life, remove mental and physical clutter so you have more resources for more fulfilling things. Go on a little vacation and make some memories, or take sailing (or piano, or Spanish, or horseback-riding) lessons and enrich your life with the money you would blow on a bed - and hey, don't compromise anything... you can still have a great looking bedroom like one of these...

Above - Image from the portfolio of photographer Debi Treloar
Above - Image from ApartmentTherapy.com
Above - A bed on the floor from one of Ace Hotel's rooms. Image from MrsFancyPantz.wordpress.com