I just like shouting, and this is one of the few legitimate chances I get to do so
!
I agree as has been said above, why not do it? It might just make someone who's approached through your blind spot notice what's going on. I've often noticed other people adjacent to me on the ramp shout it and it has just reminded me to stay clear as I do my walk-around. Harmless at worst, safety enhancing at best.
I noticed that the practice in Australia (and by the sounds of it with some here) is also to turn on strobes or other lights prior to engine starts... makes sense I guess, but for some reason our club SOPs don't call for this until after engine-run up and vital actions etc. when "ready for departure".
Andy