Because cross-country skis come in such a variety of shapes and sizes, the ski itself (combined with an appropriate boot and binding) does a lot to shape the technique of the person using it.
If you chose your ski to match a particular style of skiing, such as skating, high-performance classical, low-intensity groomed-trail touring or back-country trail-breaking on ungroomed snow, you may not notice the fact that it shapes your style. The qualities of the ski will reinforce the strong points needed for that type of skiing. Only when you push the boundaries of a ski's strong area will you start to feel it compelling you back to a stride length and rhythm more suited to its shape. It doesn't care what you want. A wide, shaped, heavily-built ski will bring you back to slower, easier strides that conserve energy over the long haul, no matter how hard you try to muscle your way down the trail in a vigorous V-skate on it.
Generally, you'll find people trying to push heavy gear into faster forms of skiing more than they will take racing gear into the puckerbrush. An experienced skier knows there are times you can have a wildly good time on racing skis on ungroomed snow, but only when the natural surface mimics or improves on the commercially prepared product. Far more common is the sight of some dogged tourist trudging along in a laborious V1 skate, wondering why anyone would spend time or money to ski like that all the time.
Because skis have such different shapes for different uses, skiers tend to collect several pairs, perhaps with boots and bindings to match. They're fairly easy to store. When conditions favor a certain type of skiing, the fully-eqipped skier grabs the appropriate tool and heads out.
