Because Thomas J. Watson was the man who turned IBM into a global empire, and Thomas J. Watson Jr. brought it into computers. They successively held the top position at IBM for 57 years. So it's a very important name at IBM, and the connection with Sherlock Holmes is serendipitous.
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Interesting comment. Of course, whenever I see pictures of the French President speaking from his office, there is always a French tricolor and an EU flag there. This may be representative of the French claims to citizenship-based nationality.