Your final point is an important one: people who grow up accustomed to low quality (or reliability) will tolerate far more than those who grew up with higher quality.
I've worked in telecom for 15 years and I frequently hear people spout that they switched to VoIP/SIP and saved lots of money. You talk to their staff people (who use the service daily, not the ones who make the financial decisions) and they'll admit to inconsistent quality. For a personal/home account, that loss of quality is a viable trade-off. But if you're running a business, you have to consider the affect on your communications with your clients. If your client calls regularly and half the time gets a low quality voice connection, in a subtle way, their opinion of your company declines.
Ultimately, just how a low a quality can we tolerate? (note that I am NOT talking about the speed of the service the voice runs over, just the voice connection quality) I am often appalled at the quality of cell calls - I struggle to understand words that are cut short or experience some sort of distortion, reducing me to guess based on context. Isn't this a race to the bottom, where everyone eventually will lose, except those who control the services from on-high? (Don't forget that downward pressure on prices eventually leads to downward pressure on your wages)
[further analogies can be made to low cost (and thus low quality) electronics that are only designed to last a short time before you have to pay again for a replacement]