You raise some very good questions. I'll try to comment.

1. Can any one tell me why more manufactures do not offer line arrays?

A lot of factors. From the marketing point of view several things control appeal such as trend toward to lifestyle solutions (limiting size in the home environment and focusing on more WAF appeal), the progression toward home theater with small speakers as surrounds, etc. Physical and cost factors include their size and the number of drivers and component imply that the their pricing would be toward the higher end audio market. Bottom line is that if technological superiority was a sole factor then we wouldn't be listening to I-pods now would we?

2. Is the production cost too high verse price point in the market?
Just wondering, with so many speaker company's offering speakers in every price range, why don't we see more line arrays?

The big name companies that sell arrays aim at the very high end of the market with 5 and six figure list prices which by definition will limit their market and overall appeal. There is certainly a lot of assembly work involved in arrays which influences selling cost. Have you noticed that your local high end audio store doesn't tend to carry a lot of more expensive inventory but rather focuses more on hot selling home theater products?

By the way, I'm confident that small niche speaker builders can be successful as they have the ability to build custom products with build to order efficiency and low overhead. Lower pricing results with limited or no dealer mark-up means better value of the customer.

Jim