I would have to dispute this, actually; Steam's current market position is currently dominant enough that it's not really worth making a PC game as anything but a hobby at the moment unless it can be sold on Steam, as it won't reach a significant enough base of customers, who buy exclusively from Steam for myriad reasons. The only exception to that are those who can exclusively provide a product that already has a strong, wide appeal, as in the case of EA.
Seems that companies like Matrix and Battlefront are able to make good profits by selling exclusively through their own webstores and keeping prices very high. So it is possible to be successful if you have a solid niche user base and a quality product.