It greatly depends. Look at what happened with Apple and iTunes. Apple created iTunes, and set up rules for music publishers that wanted to participate. They were required to sell individual tracks. They were forbidden from charging more than 99 cents per track. They were required to permit the user to burn songs to audio CDs. Etc. This ended up putting music publishers in a difficult position. Their retail distribution agreements with record stores explicitly forbade them from doing any of these things. So they either had to re-negotiate those contracts, cancel them, or abandon iTunes. They attempted to re-negotiate their agreements with record stores, but record stores adamantly refused to budge. They wanted to maintain their prior agreements that forbid the publishers from selling their music through other venues for lower prices, before the retailers could stock their shelves, etc. The record companies never budged, and went out of business thanks to their stubbornness.

Contrast that with how Valve handled Steam. Valve set no restriction on game publishers. Publishers were never forced into taking advantage of digital distribution at all. They were able to preserve all of their retail distribution contracts by screwing the customer. Digital distribution is profoundly cheaper, enables release of games a week sooner, could rely on Steams DRM without needing third party extra DRM, etc. These are all things Valve could have required publishers to take advantage of to benefit customers. But they didn't. They gave publishers carte blanche and let them do absolutely anything they wanted. If another company had been the one to become the dominant platform, it could have been more like the iTunes situation.

This is also the thing which guarantees Steams eventual downfall. Music publishers considered, and a couple even tried, building their own digital distribution service. But, the publishers were incapable (because of institutional restrictions) of building a competent competitor that would be appealing to consumers. The publishers board wouldn't permit things like individual track sales, 99 cent price caps even for popular singles, etc. Steam is a different story. Since there are literally no restrictions on publishers at all, there is also no reason for publishers to refrain from building their own separate platforms and cutting out Valve's cut of the sale. Gamers have established that they are more than willing to install and use however many launchers as necessary, so there is almost no reason for big publishers to use Steam rather than just building their own.