Yeah I know it's an old thread but had to reply. I've been in the construction trades for 30 years and regularly involved in high-end, multi-floor penthouse renovations in NYC. I'm in the electrical trades but our projects obviously intersect with bathroom renovations. I haven't seen mortared walls since I was an apprentice. Hardiebacker, Durock and similar cement boards have been the standard for over 20 years (and more recently, Kerdiboard). Yes, floating mortar has benefits such as lasting nearly forever and being perfectly flat, but most people don't keep bathrooms for more than 20 years, so the industry largely migrated to less labor-intensive and simpler installation methods. When you're dealing with these types of projects, the last thing you want is water leaking to the floors below so things have to be done right. I know this upsets dinosaurs who want to ensure job security by discouraging DIY, but things evolve. All of these new methods are adopted and approved by the TCNA.