The improvement isn’t always economic. There are other factors that make any alternative option to anything attractive, like renewability or ease of use.
It’s just that in a Capitalistic world, we often don’t see something as a success unless it is either A) Cheaper, or B) More profitable.
The only ones that seem to not be like that are hydroelectric and geothermal, since they're baseload. Which is why they're the two I advocate for the loudest -- why not use stuff that works?