[1] http://www.gog.com/forum/general/list_of_drmfree_games_on_st...
1. Publishers decide to treat all potential users as criminals, and insist on using DRM in their products.
2. Distributors accept that, and help these unethical publishers to sell those products.
3. Users accept being treated as criminals, and buy these products from distributors.
It starts from the publisher of course, but anywhere down the line, one can refuse to accept this. Distributor can refuse dealing with DRMed products from publishers. Users can refuse buying DRMed products from distributors. Any participation in that chain proliferates DRM, and one can't excuse this participation with the fact that it was initiated by the publisher.
Practically all do, I already explained above. Being unable to back up the installer is already DRM, and it's coming from Valve themselves, not from the publishers.
Always on-line DRM and such is another level of nastiness, but the above is DRM too.
Supporting unethical practice can't be excused with fear of going out of business by the way. Also, publishers need distributors and users not any less than distributors and users need publishers, if not even more. Therefore voting with your wallet (on either distributor or user level) is not senseless. Except that distributors have more leverage on publishers, because of their scale, in comparison with an individual who buys only DRM-free products. Therefore distributors can be blamed more for DRM proliferation.
Publishers of new games (especially expensively developed new games) are more likely to fear a loss of revenue, especially in the crucial early period after release, without DRM.
I'm not really sure why bigger size of the budget should reduce the common sense of the publisher. Legacy publishers are obsessed with DRM, but DRM has nothing to do with revenue whatsoever. It doesn't reduce any piracy, and only cripples the experience for legitimate users. It's stupid from common sense business perspective, and there is an increasing amount of big budget games which come out DRM free. I view it as simply mentality issue. Legacy publishers can't understand that they should start being customer focused. New ones have no issues understanding it, therefore they don't use any DRM.