How much cryptography is actually used in commercial applications? Having hundreds of pages of arcane (but highly interesting!) theory is great, but if it's not applied to real systems, like in banking, then its usefulness is limited, to say the least.
All of Part I and sections 10-15 of Part II are deployed ubiquitously in most of the world today. As is section 22 of Part III (WireGuard, WPA3, TLS, etc. use AKEs).
The rest of it appears to consist of "areas that theoretical cryptographers are refining in preparation for real world use". This is the stuff that will be deployed in the real world come 2030.
So, to answer your question: More than half of it is actually used today, and at least 80% of it will be used soon. If you're going to take a course in this, it's better to be ahead of the curve than behind it. (Otherwise, we'll all be suffering through textbook RSA ad nauseum.)
There's a conference going on right now at Columbia University in New York called Real World Cryptography if you're interested in seeing what the state-of-the-art looks like for real-world deployment.
You're being downvoted because the question looks like snark even if that isn't what you intended.
Other people have answered the direct superficial question: A lot of this stuff is used already to make stuff work. TLS (for HTTPS) has been mentioned, but if you have a work laptop it's probably using Full Disk Encryption, if you use git for revision control the content addressability that makes that possible is only safe with cryptographic hash functions, the reason a bored teenager can't listen in to all your mobile telephone calls is cryptography, the reason it's very hard (and ought to be impossible if they'd done a better job) to use a chip-and-PIN credit card without the PIN is cryptography and so on.
Now the more subtle question: Do you need any of this? Well no for a lot of jobs you don't, just as a car mechanic doesn't need a grasp of aerodynamics to do their job, but if they fancy designing jet aeroplanes that's going to be a problem. This course is about applying cryptography but it isn't an engineering bootstrap course, so it expects you to understand why rather than only learning how.
You're probably being downvoted because your post can be interpreted as incredulous without a basis in knowledge.
The answer, as others have said, is most of it. In my role in fintech/banking we are indeed using many of these things - digital signatures using traditional or elliptic curve keys, authenticated constructions built of block ciphers and macs, key derivation techniques using stream ciphers etc etc.
While we do not commit the cardinal sin (though shalt not design thy own cryptosystem), knowing how they work can be invaluable to working with them.
Perhaps on Internet yes, but you should also look up Minitel, the 1980s French interactive directory service that, among many other services, provided online banking from home. I think it mostly relied on physical (i.e. closed network) security as opposed to any cryptography.
In the 1990s, French banks apparently considered providing online banking on the open and public Internet as much riskier than on the closed and proven Minitel (and probably quite rightly so).
I Googled for minitel cryptography. The first result was your comment. I suppose that tells me there was no crypto on minitel, as well as that google doesn't miss a beat.
Edit: I don't know why I'm being downvoted.