Possibly some idiots that have never actually examined the technology...
It's a lot slower and more expensive to make a simple plastic or metal object with a 3D printer than it is to simply buy it..
The object is built up in layers a few thousandths of an inch at a time and the supplies to run a printer are not free.
Each class of printer only works with certain types of materials; the simplest use meltable plastic, others use eg. light-setting plastic or powdered metal.
Printing foods is a laboratory novelty or gimmick; you have to have the foods in some form already (eg. dried egg, "instant" mashed potato and so on) which obviously you would have to buy..
"Printing" drugs is science fiction - the chemical processing needed to create each needs major chemical processing equipment as well as raw materials...
A "House printer" exists; you can hire that, you have to buy the concrete mix to load in to it that it then extrudes - and yet again, that is not free...
The things 3D printers are really good for are engineering prototypes or just one-offs where having someone else make an item would cost far more.
They are also good for novelty items & designs can be shared so anyone with a suitable printer can make their own copy of an item - eg. like this that someone created and published - I did for a young relative:
(including it's stand [not in the picture], there is about 35 hours of "print time" to do this)
[Original article:
http://www.thingiverse.com/thing:330127 ]