IIR, close US/UK cooperation on nuclear research ended when WWII did, and the UK found itself recast as a junior bottle-washer. There likely was a whole lot of national pride behind that budgetary decision.
Edit - here's the history:
https://ukdefencejournal.org.uk/the-early-years-of-britains-...
https://en.wikipedia.org/wiki/How_the_Irish_Saved_Civilizati...
I still use physics as I'm a game developer, it's just that I stopped studying it actively, and instead focused on my computer science degree. Not to worry, I've done OK!
Hint: I did not downvote you