However, giving presentation is an important part of an academic career. As a grad student and postdoc, conferences expand your network beyond people in your lab and department. You might hope that your published work "speaks for itself", but people are people, and putting a face to a name seems to have value above and beyond the intellectual content. Later on, seminars and campus visits are important not only for disseminating your own work and building up a case for tenure, but also establishing collaborations and recruiting future grad students and postdocs to your group.
People certainly make do without giving many talks, but it usually makes things slightly harder and you might need to "hustle" in some other way to compensate: write exceptionally well, lean on colleagues to refer strong students, etc.
