The world outside the bleeding edge of tech is a really, really big place. Also, software, once written, has a way of sticking around for a long time.

Ruby has been around for almost 20 years and decidedly hip for more than a decade, and only now breaking into top 10. Delphi has been more or less dead in our bubble for a couple of decades, yet only dropping out of top ten...

I know that always looking for the most recent/hyped technology is not a good thing and there is a lot of legacy code out there, but I also know that a lot of people started using Kotlin after Google announced official Android support, so if a language rating fails to capture this, then it's not a good ranking in my opinion.

Yeah, that's the point. If Kotlin remains popular, it might make the top ten in 10-15 years.

Swift made it to the top 10 instantly, there are more Android devices than iPhones so you might expect it next year or in 2020.

I keep having to remind myself of this, trying to keep up with all the fads would be a huge waste of time whilst my customers wouldn't notice anything different.

I'm not, there is a ton of legacy code out there, some of it good, some of it otherwise.

actually PHP went up. it has generally improved as a language and its frameworks matured.