Why we don’t skip Photoshop:

3. No clients. This is a big one. 37signals is not a client services company. Rather, they build products. 37signals is a small team of people who all understand the web and web development very, very well. It’s easy for them to visualize things and move on — but it’s not so easy for many of our clients. A big reason we do visual comps at Blue Flavor is to facilitate communication and sign-off with our clients.

This is exactly what we thought when we first read the 37signals blog post. They can afford to skip comps because they don’t have clients, they have customers. It’s a subtle difference but an important one.