DRM is a way to ensure those who put hard work into producing a product get their reward.
Only partly I'm afraid and I've no objection to that
mixture, it also allows the publishers to manipulate the market as they did for years with music and videos, just ask yourself this, why are videos zoned.
Most people don't object to paying a reasonable price for something but do object to being ripped off because they live, say, in Europe and find people in India or China can buy the same product for half the amount.