Yes its evolution, but mainly marketing.
Global business is and has been in downturn of late. So, how do you enthuse customers and investors to part with their money? You come up with something new and innovative that they can believe in, then market and sell the hell out of it.
26′ wasn’t going to ignite the steady dribble of volume sales, and other technology attached to 26 is too expensive to mass market and sell (adaptive shocks for example) to anything other than the top tier.
A company I know of that has spent the last five years trimming itself down to increase cost efficiency and report higher margin, hss now realised that investment in effective Sales and Marketing surround new innovation is the only way out to create increased revenue.
Et Voila.
But as said above, its good for us all to have a choice (as long as the spares list keeps up).