Several reasons. Here are are the ones I can quickly think of: 1. Lots of money for a product that customers can't really inspect before paying. 2. Same as #1

Several reasons. Here are are the ones I can quickly think of: 1. Lots of money for a product that customers can't really inspect before paying. 2. Same as #1, but simpler: lots of money. 3. The customer. Feature-creep and a lack of vision can really dismantle a project in it's nascent stages. I've seen many a project fall victim to this. 4. Lack of testing. This is usually caused by #5 and #6 below. 5. Deadlines + customer's constantly changing scope can == bad code (at times). 6. Like @coderdude said, the field itself (and it's workers) are generally immature (and therefore haven't learned best business practices - or best practices at all, for that matter). 7. Web DESIGNERS != Web DEVELOPERS. Many, many customers don't know this (you'd be surprised).