Why is MATLAB a worthwhile investment in electrical design?
I am slightly bias'ed on my views of Matlab as I have been using it for decades. I am also part of their advisory board. 

The immediate benefits of Matlab is job opportunities. Being able to put onto your CV that you have x number of years leveraging Simulink(tm) in a multidomain model to optimise the time to market of a new program speaks volume.  

Matlab at its core is a programming language written by mathematicians for mathematicians. There are aspects of matlab-script that appear really poor design semantecs but make sense from a mathematical perspective.

Personally python+numpy+scipy+matplotlib > Matlab. If you add Simulink... I can describe a 30kVA BLAC motor-drive (3phase in, inverter, control, motor, loading response) in python and provide results comparable to the real system and a simulink model. That doesn't mean others would easily be able to take my code to determine system responses.

Now Simulink... Simulink is a very very powerful suite of tools to simulate systems. If you are a circuit designer you may question the usefulness of it over say... SIMextrix but thats because SIMextrix is a spice simulator and Simulink is a systems simulator. Simulink can simulate electrical circuits, hydraulic, mechanical, fluid etc but it does not do this as well as dedicated applications. However those dedicated applications do not describe other physical domains. So the moment you need a cross-domain simulation what are you going to do?  you need a suite that can cater for this to then provide domain-specific information to the more detailed design suites.

Second to this is the concept of "model base design" where a simulink model captures the intent of a system model for requirement management to finally facilitate autocode generation. When subsystems/blocks are linked to requirements (say in DOORS or ... excel if you must) a design team can gain coverage and provide an audit-able trail if the business environment you operate in has some sort of agency oversight