I don't think it's just laziness. I think these interstitial modals are implemented under the (somewhat misguided) assumption that it's possible to force a user toward a particular type of interaction by forcing that interaction down the user's throat.
Realistically, whacking a user in the face with a "Follow us on Twitter!" modal will increase the number of people who click the "follow" button. That's something that's easy to measure. It's a shortsighted approach, though, because you're trading short-term gain for a less quantifiable long-term erosion of trust.
I've found that clients that don't understand why it's important to build long-term trust are usually just worth avoiding... both as a customer, as a user, and as a designer. Eventually, but too late, they'll finally get the message.
I wish the author would point out exactly what qualifies as a modal. Is it anything with a close button in the top-right? If so, popovers could often be considered modals, and they can be used really really well to make an application more usable.
Modals, if done full-screen, also provide focus. A great example is photoviewing. Those are officially modals, but are necessary to provide the most screen real estate and focus the user on one particular task.
Hey Chris, I was more strictly talking about modals as a tool for flow interruption. You are right, galleries while in some sense of the word are modals do not fall under the scope of this article.
I'd be curious to see some examples of in-app modals done well (e.g. non-marketing sites).
Thank you! Glad there is someone who feels the same. Most of the time there is a better solution that doesn't involve modals. They are intrusive, agressive and work terribly on mobile.