IMO they are exactly like military-industrial complex where increasingly complicated software will need newer and complicated hardware because "customers demanding it".
This is very far from current state of affairs, where for almost every possible kind of software there are a lot of different developers with vastly different products, different designs and ideologies. They may not be as well-known, but they exist in their niche, and you can definitely vote with your wallet for one that looks to your liking.
Extreme example - mobile todo app. I think that one in ten professional developers released one to app store just as part of his portfolio. And users still choose apps with mainstream design, look and feel. If that's not voting with their wallets, what is?
I'm tired of repeating this, but here it is:
Voting with your wallet. Is. Bullshit. Consumers don't pick from the space of all possible products, they choose from what's available on the market. Especially in software, it's producers who collectively determine trends. If they all fall into a fad, customers have no way of saying no.