I think it's just a matter of visibility. It takes a while to change the public's buying habits from brand to brand and unless Mizuno has a bunch of tour pros rush to play some new driver, there won't be much stimulus for the public to do it either.
For a long time, TM drivers were looked upon as being the more innovative in the business. They did things to make sure their drivers were more recognizable from a distance too. First white driver... M1 and M2 models with the white paint bar across the front. Their plan is reinforced by the high number of tour pros they endorse.
Add to all that the simple fact that we, as golfers, often tend to buy certain clubs for the wrong reasons, sometimes based on who we like that plays them. How many people have you seen with classic blades in their bag, but who definitely need super game improvement? The human ego is a terrible thing.
One brand without the big market share has an awful lot to overcome just in visibility and human nature, even if they make the best clubs in the industry and we all know who that is.