I don't know. Financially it would be a very smart move. They would probably lose some loyalty with fans though. Can't say I would pay for it either. I prefer the bonus deal with PS plus rather than kissing the companies ass for a service that should be free.
Why should it be free? Considering everything that is included in the service, I think £40 a year as a subscription is pretty fair. If they are providing you with a product or service, why do you think you should get access for nothing?
What exactly should I have to pay for? I paid for the $59.99 game which should give me access to the servers the developers/publishers set up for me to play the game on. I shouldn't be forced to use a console manufacturers online structure because they want to make a profit on something that should be free.
You didn't really answer my question, rather just repeated your belief that the PSN and Xbox Live should be free. If these services were simply online connection I would be more likely to agree with you, but in the same sense you could argue that your internet service provider should provide your connection free of charge.
These services go beyond just providing that connection though. I am unfamiliar with the PSN, but Xbox Live offers various streaming services, game content including DLC and full games, access to TV and radio amongst other things. Microsoft is coevering their costs of providing this service plus a mark-up to make a profit, which is seperate from the way Activision, EA etc service the online content of their own games (Microsoft have also not implemented the online pass in the same way EA has either).