It's really a marketing question. Salesmen haven't figured out a way to hype 1x. You do find 1x on work road bikes—city bikes and folding bikes (or time trial bikes for that matter)—just not on play bikes. People who bleed their brake cables aren't going to embrace the simplicity and easy maintenance of 1x. That's for people who use their bikes on the job. And it's hard to package it to sell: a new rear derailleur with a deep pitch but less wrap? a wide range cluster with subtly different spacings? a crank with a subtly optimized chain-line? Anyone with a handful of spacers and some Allen keys can try 1x for themselves.
A personal anecdote that will date me: Back in the 10-speed era, I crossed the continent. I set up 1/2 step gearing that gave me about 38" to 100" gears because I could use a prestigious Nuovo Record crank, and believed cross over gearing with common Japanese "touring doubles" (now successfully re-marketed as "compacts") was inherently wasteful. My low was higher than current racing lows, but we didn't spin uphill and state highways are graded for trucking. By the end of the trip, I wasn't bothering with double shifting on the lows and essentially using 7 gears. In retrospect, cross over gearing would have been simpler and just as effective.
My point is not that you need few gears. I love smooth continuous cadence enhancing gearing. Rather that one should gear to purpose.
How gears should be arranged
Gear and cadence define speed, but external conditions—headwind, tailwind, uphill, downhill, scorching heat or bitter cold—define how much wattage you can output and how much you need. Since that is not predictable, you want gearing to offer you a small, consistent increase or decrease in effort wherever you find yourself on the range. However, one tooth steps at the high end won't match one tooth steps at the low. This is partly because of the math: 12 to 13 is the same jump as 24 to 26; And party due to going fast in high gears and slow in low gears. Usually this means you are fighting the wind in high gear and gravity in low gear. Effort against gravity is constant. Against the wind it is the square of the velocity. Small changes in speed in the wind, will require twice the change in effort. In other words, a 10% increase in gearing at the high end will be equivalent to a 20% increase at the low end. Of course, there is always a mix of wind, road, and gravity resistance so the difference will be somewhat less in practice. This all works out to 2, 3, and 4 tooth gaps in the bigger cogs of 11-30something clusters, which is why they are sold that way.
The limiting factor in 2x crossover is the front derailleur. Empirically a 14-16 tooth jump is the reasonable max from both a mechanical and physiological view. That means your gearing will cross over after about five gears. Thus, ten tightly spaced gears at the top, the remainder stretched out to cover the lower part of the range. Each extra gear on the cluster will add to the overlap with the big ring, and to the density of the low gears with the small ring. A little overlap is useful as it allows you to delay the double shift till more convenient. With nine speeds you make some choices. Thirteen is an embarrassment of riches.
With a 13 speed cluster, 1x is quite reasonable. Sure, it doesn't give you the 18 speeds that a 2x cross-over would, but you can start stretching out the gears sooner, and you will miss less that it first appears—while saving a bit of weight and that inevitable double shift.
I think the industry hit a high point when Campagnolo repackaged their cross-over triple with a 30 tooth low and rebranded it a "road triple". The trick is using the third ring to forgo cogs in the back. You can match the density and range of a 2x11 using an 8 speed cassette, while benefitting from greater durability, reliability, and tolerances of an 8 speed. The chain-line is better (not, as often stated, worse), the weight penalty is less than it appears as the cluster is smaller, the chain wrap only a link larger, and mostly comes down to an extra ring and bolt set. And shifting is buttery if you sensibly use a bar-con and, ahem, a chain watcher.
Back to the future
All this assumes cross-over patterns which makes sense with dense cassettes and mechanical shifting. Who needs to memorize double shift patterns? But it's trivial with a chip and apparently the pros are already using Alpine (X and 1/2 step gearing) pattern sequences programmed in. Not sure what happens if you hit the shift button three times, but I'm surprised it isn't being pushed more. I think the future holds 1x, 3x, or electronic 2x.