[keewee7]

I am surprised that there isn't open source alternatives to Simulink, Stateflow etc.

One reason Matlab is popular in academia and industry is because someone who don't know C/C++ (mechanical engineers etc.) can use something like Simulink to program real-time systems on microcontrollers and FPGAs.

[IshKebab]

There is Xcos, but IIRC it's pretty poor compared to Simulink. Honestly Simulink is super niche. I'd guess there are 10 times more MATLAB users than Simulink users. Not surprising there aren't many alternatives.

I think a bigger reason MATLAB is popular is that it works really reliably, it is very well documented, it has a ton of complex algorithms and functions built in (or available in toolkits at least) and the interactive GUI works very well.

There isn't anything anywhere that comes close to MATLAB's plotting abilities. And scientists do a hell of a lot of plotting.