Academia in Britain was intimately connected to membership of the church and, thus, to the ability to speak Latin to hold services. It held on beyond that tenure out of both momentum and prestige.
All academia used latin until quite recently. Because all books were written in latin.
Why do you think all animal species have a latin name? You think the ancient romans classified them?
That was true in medieval times. From the start of the early modern (e.g. Henry VIII) the Church of England used English for services.
The prestige also accrued because it was the language of the educated in Europe for a long time.