Free Pascal

On benchmarks its on par with C++ and even lower on memory.
Why isn't it used much?

While I can't speak for anyone else, I don't use Sepples because it is stupidly limited, pedantic, annoyingly verbose, makes superfluous use of semicolons and templates, requires extra work to use any form of meaningful abstraction, and because of all these things, it's also unpopular (and rightly so) - thus it is poorly supported in development environments.

In short, it's a complete pile of month-old dog shit.