One of the problems with who owns the material produced by a prof for teaching a class is the fact that people move around.
So a prof starts at school A. Takes some existing material. Adds some stuff to it. Moves to school B. Continues to use and add to it. Moves to school C.
If school B suddenly tells the prof they can’t use the material since B owns it, and sends a threatening letter to school C to make sure they enforce it (because that’s what lawyers do- send threatening letters to everyone).
Now it’s a mess. Maybe the prof asks A for help to prove that it is mostly stuff from that time period. And A decides they need to send out letters to everyone. And on and on.
Schools suing other schools is to be avoided.
So they don’t really want to kick this hornet’s nest.
OTOH, they really want a copy of all course notes, assignments, exams, etc. for the next person who will teach it. It’s a quid pro quo. We don’t exclusively claim it and you won’t either.
Similarly, patentable ideas might have been developed over the years at more than one school. So they only got really serious about latching onto those once the stakes got high enough to endure the hornets. Computer Science was one of the key fields in making them realize the money involved. We and the Biologists and such say “You’re welcome.”
The last school I worked at rolled out a required form regarding patents. Even for existing faculty. “Don’t sign it? Well, we can’t fire tenured people but then we can not pay you, kick you out of your office and, worst of all, take your parking space.”
It was horrible. You submitted your idea to their IP lawyers. They had a year to decide what to do: file on your behalf and take half or let you have it. Um, this was bad before but now it’s a first to file system. You do not wait one day to decide to file or not.
(And I mistyped “Defintion” instead of “Defnition”!)