Actually I think I don't. PCs are quite cheap nowadays and can do a lot more than consoles, they can be modified, they are more custimizable. Console games are also a lot more expensive than PC games, at least in some countries. So I don't think people will have a problem affording an OK gaming computer if they perhaps save a little bit more, but catch up the money on the games so to say.
The advantages I can see with not having consoles are that without consoles, developers can focus on one platform, that will mean less work for developers, less money they have to spend on production, wich means more money for productions, more time or cheaper prices on games with same quality. I'm aware that perhaps medium-end computer would rule the PC market, however it would still, I believe, be easier for developers to develop on one platform and add some extra eye candy for those with high-end computers.
Developers would also have more time to optimize games for PC, meaning medium-end computers hardware would be used better. I believe developers focusing on optimizing for medium-end hardware would lead to a faster graphics evolution in games.
Developers would not be limited by the limitations that come with developing for consoles, for example small amount of memory. Neither would they have to pay royalties to Sony and Microsoft. All in all they would probably make bigger profit than today. Also it would do all the hardware manufacturers good, there would be a higher demand. Perhaps more gamers would learn how to build their own computers, and gain more knowledge of computer hardware. HP, DELL and other computer companies are quite expensive in comparision to building your own computer.
I think more people would take the step to start their own game company because they no longer have to think about gamers being spread over multiple different platforms. Developers would also be less careful about "taking chances", trying new formulas in games, being innovative because once again having gamers on one platform would mean that all gamers who might be interested, no longer are spread out over three different platforms, but one, PC. Also the production cost would not be as high as today, making risks less of a problem.
Today Sony and Microsoft have to pay hardware manufacturers lots of money for them to produce special hardware. Because if they put hardware that already exists into the consoles, people would know what's inside and by knowing that they would compare prices with building a computer with better hardware, also they would compare the consoles with ones each other and have more concrete evidence of which one is better. That's also what makes it hard for developers, they have to code for different hardware architectures.
Come to think of it, it's probably good for gaming developers in a way right now, at this very moment, that there are consoles, because if there weren't they would have to change to programming for PC-games, and there would probably be enough in the game company already, meaning them losing their jobs. But the amount of PC games companies would increase, so they would probably find jobs easier.
This is what I can come to think of right now, still I'm not sure how it would be if consoles didn't exist, this is only what I think might happen.