To get the best experience, attendees should join sessions with a supported browser. When attendees join with an unsupported browser they may still be able to join the session but their experience won't be the same. Sometimes older devices won't let users upgrade their browsers. Sometimes users don't realize their browser isn't supported and reach out to their support desk when they run into issues that could have been solved by a browser update.
Our user groups suggested we pro-actively inform users and encourage them to upgrade, in order to lower case load and improve their experience. We still let those users enter the session, but at least they know what they can do to improve their experience. Thank you for your feedback, we're happy to bring this to you to make the back to school experience smoother.