Motivations for PhD students to present at a conference session for work in progress I am currently helping to run a doctoral colloquium (DC) for a conference that's going to happen remotely.

For this DC, we are accepting work-in-progress papers whose first or sole author is a doctoral student or candidate. Also, this DC will give the opportunity for them to briefly speak about their research or proposed research in a three-minute thesis (3MT) format/style, supported by a single slide or other visual aid, before engaging in a moderated discussion with one another and with the audience.

As part of that planning, I'm trying to understand more the side of the students to present at the DC, as would like to have them interested in joining the conference and also being engaged. What are potential motivations for a student to present their work in progress in such a format?
These have been part of ACM conferences, such as OOPSLA, for a long time. They give students, especially those nearing completion, a source of feedback on their work. Typically the participants will be not only the students but at least some of their professors and some others interested in what is happening with current doctoral research. 

Before I retired we always encouraged our doctoral students to develop an "elevator talk" in which they could explain the essence of their research in the time it takes to ride or wait for an elevator, say about 3 minutes. It is an extreme form of abstraction that is useful for a student to consider. 

But the potential for (a) a bit of early visibility and (b) a bit of independent feedback are worth the effort. 

Some of the conferences would also have some scholarship/travel money for attendees. And the student could, then, also attend the rest of the conference and build a circle of contacts. 

I don't know how a remote version will work, or whether it will have enough of the right elements to make it viable, however. But it was valuable for face-to-face conferences.