That's a false analogy. A horse-drawn carriage is a fundamentally different mode of transportation than a car, but a BlackBerry is identical to any other smartphone except for the small keyboard on the front.
The reason BlackBerries are not popular is because early touch screen smartphones were simply so much better than the BlackBerries of the day, and that set the precedent in consumers' minds that smartphones are slabs and smartphones with keyboards are bad (as evidenced by the people in this thread). But modern BlackBerries are just slabs with keyboards. If BlackBerry didn't aim their company at the ground at full throttle, the present phone landscape might look a lot different.
Also, most people simply don't need a smartphone with a keyboard, because all they use it for is SnapChat and FaceBook. It's like saying mechanical keyboards are inferior to rubber membrane keyboards because only a relatively tiny portion of the population uses them.
And yes, people are buying them. Not many, but it's apparently enough to be profitable, because TCL keeps releasing new models. Not on the levels of Samsung's S or Apple's iPhone devices obviously, but that's not what matters. (Close to a million KeyOne models were sold in 2017, but I don't know what the current numbers are like.)
I'd actually be curious how many people are buying them - it wasn't enough to save RIM. I think not as popular as the iPhone is a pretty big understatement and thinking that's mostly about Apple's marketing comes across as pretty clueless to me.
Some people still prefer horses to cars, but it'd be a generally bad idea for someone getting into the transportation business to focus on horse drawn carriages.
Popular doesn't necessarily mean better, but when you're an extreme outlier compared to what's dominant in the market and what's dominant in the market directly out-competed your preference when it had dominant market advantage, there's probably a reason.