If you have an alignment problem, the wheels may not be tracking "straight" and will wear the tread in a "sawtooth" fashiion, or what we usually call "feathering". Running your hand along the surface you will feel how the leading edge of one drops to the trailing edge of the next, when they should be all at the same level.
Also, having the tires not balanced (though you should notice this as it will cause a shaking in the wheel or a thumping feeling) or having the pressure set too high or too low will cause uneven wear.
In addition, there are just some tires that are known to wear poorly. On tires that are standard issue on a vehicle, these often become known at the dealership, whereas at a tire store they put on so many brands and makes of tires they often don't see another of the same set for a long time.