I'm echoing what Alex, Jeff and Sebastian are saying about the time/cost/revenue implications of having a software service company.
As for why service-based startups are less discussed on this forum, and whether such ventures are treated as startups at all:
Vivek Wadhwa wrote a very interesting and informative article last week on entrepreneurship for Techcrunch: you can find the article here.
In this article, he makes the distinction between "replicative entrepreneurs" (i.e., those who start a new business in an established service or field) and "innovative entrepreneurs" (i.e., those who create an entirely new product, service or technology).
Product-based startups fall into the latter bucket. Service-based startups in the former.
Speaking primarily for the SF Bay Area (including Silicon Valley), the emphasis and interest has always been on innovation - new ideas, new products, new businesses, new ways to change the world. That's the mindset and the motivation here - people build new companies to scratch an itch.
My fellow posters have already covered the pros and cons of a service-based startup. As far as product-based startups go, the pros clearly are:
The biggest con is that your product may be a failure, and you are forced to look for gainful employment :-)
This is where the Indian psyche and mentality clearly shows through (I'm not being disrespectful here, because I'm from India too) - we definitely value a steady paycheck, and while we are risk takers, we only do so in fields where we are certain of returns. So the risk we take is to start a company, but we hedge that by building a company that has a high(er) probability of getting established, and a high(er) probability of steady revenues.
It's a proven model - you only have to look as far as Infosys, TCS, Wipro and any number of other Indian service-based companies who have made it really big.
However, because of the issues of scale and also because of the perceived lack of innovation, this isn't appealing to a lot of people. Here in Silicon Valley, you'll hear the "two guys in a garage" story ad nauseum, because out here that is an inspiration - HP, Apple, Yahoo, Google, Facebook, Twitter et al.
I hope that answers your question - neither product-based nor service-based startups are "better" than the other, and I'm not taking sides. It is all a matter of perception. Different types of people get passionate and enthusiastic about them, and it's up to you to choose the path that makes you happy!