The first reason which springs to my mind is that, in the last survey,

In order of frequency, we include 366 computer scientists (32.6%), 174 people in the hard sciences (16%) 80 people in finance (7.3%), 63 people in the social sciences (5.8%), 43 people involved in AI (3.9%), 39 philosophers (3.6%), 15 mathematicians (1.5%), 14 statisticians (1.3%), 15 people involved in law (1.5%) and 5 people in medicine (.5%).

and I think it'd be very difficult to become a computer scientist or a hard scientist without learning to at least read English. (For example, graduate-level physics textbooks, when they're translated in Italian at all, are, like, five times as expensive as the English originals. And good luck finding translations of (say) arXiv preprints -- I don't think I've ever seen any such thing.)

ETA: See also Weber (1995):

From, a certain level upwards, in business, sport, politics, science and many other fields, a knowledge of English has become not a matter of prestige but of necessity. Also: the level at which this occurs is moving ever downwards.

In science and technology the grip of English is complete. With growing computer sophistication it is becoming easier to put even the most awkward languages and script on screen but that does not alter the big picture. The Chinese trader, scientist, manufacturer who wants to talk to his foreign contacts is not helped much by even the most carefully presented Chinese characters on his screen. He has to tell his non-Chinese customers - in English.