When will people stop using message boxes in their plugins!!
Running a modal loop will crash the host if it tries to unload your plugin while the loop is running, and popping up message boxes will annoy your users - don't do it! If you need to show a message, embed it inside your plugin's window, and if you absolutely must pop up a window and make it modal, do it without running a loop.
ups, sorry to upset you, but to answer your question: people (me) will stop using it, as soon as there is no need for me to display development exceptions anymore. Precicesly: soon.
Until then: embedding debug messages in the UI is a bit of a development overkill. I just need my plugin to display a message to me, and since am I currently the only user (debugger) it will only upset me, and thats intended.
And for production software its probably also not a good idea to post messages in the plugin UI; the UI might be closed. So either the message is not important - better discard it, or it is and then the developer should find a better place to display it.