Space. Like money, it's one of those things you never really have enough of. You need a printer, a fax machine, a copier, and a scanner, and they all take up space.
But that doesn't have to be true. Epson offers a series of multifunction printers like this one that can do it all without taking up much more space than a traditional printer. Inkjet printing gives you high-quality printouts, but also crisp copies that don't have the problems thermal photocopiers sometimes have.
The scanner lets you record your documents, and the fax portion even lets you send facsimiles of those documents, all in one compact unit. Now, you know what you need much better than we can, but it costs less than four devices, uses less energy and space than four devices; this might be just what you need.