It is just as likely to find a researcher who does not talk well as you could find an artist, a designer, a handyman, a farmer, or any other person who is more dedicated to their craft than in developing and refining their presentation skills. The person simply doesn’t perceive much of an advantage, or at least is not burdened with a disadvantage, in giving effective presentations. You tend to find great speakers in places where being a great speaker grants an advantage. Salesmen, client-facing individuals, CEOs, angel investors, marketers all benefit from having great presentation skills. These people tend to also advance their skills by continuing their education or participating in training related to being an effective presenter, such as attending a free Toastmasters meeting, or by participating in pay training. And then of course one’s personality and life experiences in public talking/presenting will change things up further.