In a virtual or regular classroom environment, building personal connections with students is one of our primary goals. Screencasting enables instructors to deliver content and present their personalities for students.
It also frees you up to monitor the class while the screencasts are playing.
Screencasting works very well for synchronous (physical or virtual) as well as asynchronous (not at the same time) communication. I know my students enjoy the change of pace that comes with watching me on video, even if I am in the classroom with them.
For example, in the video production and coding classes I teach, I create screencasts to support the work they do. I started doing this prior to virtual school to help students view instructions multiple times at a pace that works for them and lets them rewatch as needed.
When virtual school time came along, I realized these screencasts gave me a whole additional content delivery method.
There are multiple recording options out there from free to paid. I use a paid version for my professional recording, but use free ones for more casual feedback to give to students.
In general, the free versions are fine.