I know why Linux hasn't gained mainstream popularity with the normal consumer. And i know why it never will.
It's because it doesn't cost anything. People associate a higher cost to higher quality. Because Windows 7 Ultimate has a price tag of A$268 the normal consumer will identify this as superior in quality than, say, Linux which is completely free.
Also lack of advertising from a major corporation like Microsoft means Linux has no awareness to the normal consumer.
Basic micro-economics