I also agree that breaking zoom is a silly thing for designers to do.
But small font sizes, and expecting the average user to know that they can zoom, is wrong.
All three are symptoms of a bigger problem - some designers are either ignorant about usable design, or just don't care about a significant portion of users.
I'm all for never overestimating the technical literacy of one's users, but .. really? The average person doesn't even know they CAN zoom? That seems an "ignoratum too far", like not knowing they can alter the volume on their stereo.
Touch screen devices make it ridiculously easy, too. Surely the average user has worked out by now that they can change the size of a web site they are viewing.
I strongly believe, but have nothing to support it, that most people don't know they can zoom their browsers.
Average desktop user does not know how to zoom. I have done hundreds of usability tests and user observation in my time - the number of folk who know how to zoom text is vanishingly small.