What a strange question!
Why you should do the course:
You will learn the correct etiquette and procedure for radio transmission – the first day you have to talk to authority on the radio you’ll crap yourself
(I suppose you could practice this at home after doing the internet courses.)
When you pass the exam at the end you can:
Be happy that you have a certification.
Apply for a Ships radio licence; get a call sign and MMSI number
Input your number into your VHF and use the DSC distress facility of your machine (God Forbid!)
Your call sign will be looked for if you ever help out with a situation on the water.
Speak on your radio because you are entitled to
It has already been pointed out that it is illegal to use a radio without an operators licence. It is also illegal transmit without a ships licence. Nobody has ever been prosecuted and I’d say nobody ever will.
To me it is good to be “professional”. It is also something nice, enjoyable and useful to be doing during the winter months!
Why you should not do the course: