I got a couple. They were cheap. Plus, perhaps like you, I wanted something to blow the rust off my soldering skills – assembling a shield from a kit was just the ticket.
But so much depends on what you want to do. Again, Arduino is cheap. Get a basic Deicimilla, fire it up, write your “Hello World.” There’s time enough to dream up some project you want to do. You can stick wires in the headers easy enough to try out LED’s, connectors to other computer gear, and so forth.
For me, I walked into Arduino with something I’d been meaning to do for years…strike that…decades. Which was a simple MIDI command generator. For me, a basic shield turned out to have the space I needed to hook up my few components.
You might, however, be more interested in robotics. Or a POV project. Or a remote sensor. Or integrating a surplus joystick into a flight simulator game. Or… In any case, there are not just less-generic shields out there – sensor shields, motor bridges, and the like – but there are even specialized Arduino clones; from Boardinos to Lilypads.
So before you really get into asking whether you NEED a shield, you might want to get more idea about what a shield will do for you.