beta updates are a many, many, many step process, especially for iOS users with chrome as their default browsers. Most app betas these days allow for in-app updates for beta builds, for this to happen the testflight SDK has to be included in the beta builds.
This should drastically increase the uptake rate for active beta users staying with the most current build by reducing barriers to doing so.
http://help.testflightapp.com/customer/portal/articles/829568-how-do-i-implement-in-app-updates-