I take issue with the idea the DIYer's are more interested in value than quality. Not to say that none are mind you, but as I am involved in the do-it-yourself market I would like to offer some reasons as to why this is not always true.
Some homeowners simply have a distrust with regards to contractors (like me with an auto mechanic). Not all contractors have the homeowner's best interests in mind. Others simply enjoy the process of learning a new thing and gain a sense of acomplishment when the job is complete. Because labor can more than double the cost of materials homeowners doing the work themselves have more room in their budget to purchase higher quality materials. Not to mention the tools they will acquire from the savings on the job.
This is not to say that every potential home improvement can be tackled by the inexperienced DIYer. There will always be the need for profesional installers