To get back on the original topic for a mo, I think its indicative of the prevalence of mix powders by their almost exclusive use in recipes posted on this forum. Not only that, but the majority of BIR related books/ebooks/websites use mix powders.
Add to this, the experience of those witnesses who have been lucky enough to work within a BIR restaurant or T/A. Without exception (I think!), all have spoken about the use of mix powders.
I use Abdul's 8-Spice for my day-to-day curries, while I make up spice mixes for out-of-the-ordinary curries etc. For traditional dishes, I just follow instructions which invariably involve the use of a number of single spices.
The only other exception, for me, is the use of spice pastes which, after all, tend just to be spice mixes with liquid added.
My tuppenceworth, Stu,
