All the incessant wheel size fads is entirely down to marketing BS, and nothing else.
Those of us who have defiantly given the marketeers the middle finger and refused to "upgrade" from 26" to whatever size they want to sell us this week, are just ignoring the noise and carrying on regardless. At the lower end of the market, 26" is still the dominant MTB wheel size even in the UK, and low build budgets don't run to disc brakes so rim-braked 26'ers aren't going anywhere even though the BS merchants would have us believe they belong in a museum.