Well, its not banned, it is cheap, it is used in commercial buildings and, even if not officially, it is sometimes sold as away of dealing with a roof that has a lot of slipping tiles as it consolidates them and is cheaper than re-roofing.
The only people encouraging its use are those who install it!
It is like so many things, properly used on suitable roofs, where there has been a thorough roof survey and assessment before hand, it is probably as effective and undamaging as any other method, but when products, initially developed for one use, are seen to have another use, without there being any proper technical assessment, problems arise.
At the end of the day, that is what lay behind the cladding scandal, a real and genuine need and desire to make buildings more energy efficient, followed by looking around for ways of doing this and seeing materials developed for another use that they thought would be ideal for the job and using them without them being properly assessed for the new use.