Marketing or not, here's the synopsis of my rant: choices are good, and you and I are living through the by far the best time to ride bikes since the late 1800s. Certainly the best time to ride mountain bikes. The diversity of options and choices to get a bike that is fun for you and your terrain is ASTOUNDING.
Of course, we had lots of choices back when I started riding in the 90s:
-26" wheels or 26" wheels. Oh, and the Beast o' the East. You young'uns can "google" that.
-1.9", 2", or even, if you were some kind of lunatic, 2.1" tires with medium to large knobs.
-71/73 NORBA geometry or... 71/73 NORBA geometry. With 425mm chainstays and a 12" BB height, no matter how short or tall you were. Want long cranks? Tough cookies, have fun bashing all those rocks. Keith B made some steeper angled frames with 32mm low-rake forks on them, though, so if you were cool you could score one of those and go OTB a lot.
Want to ride on snow? Sand? Carry a bunch of crap with you and go for an adventure? Too bad, you'll have to adapt some panniers from your old touring bike and hope they last the trip, and walk through the sand and snow. Or stick 2 rims together and lace them to a tandem hub, and install 2 tires at once, like the Iditabike guys used to back before fatbikes were a thing.
My point is this: the sheer number of options out there is awesome. It's amazing. And the fact that you can independently select the outside diameter and width of your tires is a big big deal to me. Let's look at some commonly available sizes:
-24x1.5-2 are available though mostly used for BMX cruisers.
-24x4 are being made for the new Specialized kids fatbikes. They will be very useful for small adults who want to ride on snow as well.
-26x1.8-5 (OD from 25.5-29")
-27.5x2-3.25 (OD from 27-29")
-29x1.8-3 (OD from 28.5-30.5")
-And of course 36x2.3!
That means almost no matter what size you are and what geometry/terrain you prefer - you can find a tire/wheel combo that will suit you. That, my friends, is amazing and worth celebrating. If that's "marketing hype", I'll take more, please.