Naively, because it only takes two suppliers in a market, for consumers to start playing them against each-other by switching to whichever one plays more to con

Naively, because it only takes two suppliers in a market, for consumers to start playing them against each-other by switching to whichever one plays more to consumer preferences at any given moment, incentivizing the suppliers to compete to satisfy that consumer preference. Like a classical "race to the bottom" that lowers prices, but with some other factor that consumers care about instead of cost. (Of course, this assumes people bother to switch. In reality, this isn't even true in oligopolist party politics, let alone in oligopolist markets. In practice, there need to be a lot more, smaller options before switching costs are forced down enough to encourage people to switch. In phone markets, this looks like how people switch somewhat easily between different Android device manufacturers for their next phone. If we could get phone Operating Systems working like that, we'd really have something!)