Let us see the following two scenarios to understand why do web designers create ugly sites:

Here's the ideal:

Client: Hey, designer. Here's an outline of what I want, and all the information you need to do a great design.

Designer: Sweet! <days later> Here you go, a beautiful website.

Client: Awesome, it looks great!

Here's the reality:

Client Representative: Hey, designer. Here's an outline of what I want, and all the information you need to do a great design.

Designer: Swe--

Boss: Make sure it integrates with our CRM, CMS, and our proprietary payment processing software.

Marketing: We'd like to see three kinds of carousel widgets so we can feature content prominently. The right column will sometimes contain adwords banners. Make sure you integrate our web analytics, A/B testing, CRM, and content delivery platforms.

Sales: We need to be able to rotate vendor logos into our header. Also, forget what marketing said, the right column should be reserved entirely for a client status widget. Can we change the first three tabs in the nav to "Features," "Advantages," and "Benefits?"

IT: Nobody cleared any of these technologies with us, and three of them don't work with our stack unless you write your own custom adapters, so no one will support them if you design around them. Except you. What's your home phone number, by the way?

Finance: How are we tracking the site's ROI? We need visibility into profitability both per-category and per-page, so we can incrementally adjust and improve.

Customer Service: It also needs to be as simple as possible for our idiot customers...and make sure there's a self-service knowledgebase, and our phone number is hard to find. Except in Europe.

Legal: We have to vet all the graphic and copy choices to make sure we aren't infringing on anything.

Localization: By the way, all those pixel-perfect UI elements you created? Turns out that 7-letter word in English translates to "Produkteinführungen" in German.

Accounting: And your budget is $500.

Client Representative: And here's all the info you need to get started. <e-mails 2-page PDF>

Then repeat after each iteration.

Credit and Source: Andrew Hamada