Just because they're marketed as "MMO" mice doesn't mean that is their sole purpose. You'll be hard pressed to find a mouse on the market with more than 6 thumb buttons that isn't marketed as a "MMO" mouse.
With 12 side buttons + the mains you could easily type with the mouse by assigning the first half of the alphabet to individual buttons and the last half to modifiers (like hold Alt for N-Z) and voila. Well, not easily type, but you could eventually get there and it would be a neat skill to brag to your friends about.
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