Unfortunately, lightbox-style galleries still behave inconsistently across hardware/platforms/browsers and often break. And, you're right, many people find them annoying. But as a developer who recently converted a portfolio site, I can tell you that it tremendously simplifies the code needed to present a gallery of images, making a portfolio-oriented site much more easy to update. Also, clients tend to go ga-ga over the slick eye candy (thus decreasing the demand for Flash, so it's not all bad).