The short answer is that UITableView is an inherently synchronous API whereas the React Native bridge is asynchronous -- UITableView calls cellForRowAtIndexPath:indexPath: and heightForRowAtIndexPath:indexPath: and you need to respond synchronously with the view for and the height of that cell.
One of the problems with this is that under the current React Native architecture we would need to break the async bridge model by synchronously calling into JS in response to these methods. So some people are experimenting with a slightly different architecture that would allow us to respond to them synchronously from the main thread, which seems really promising :)
One of the problems with this is that under the current React Native architecture we would need to break the async bridge model by synchronously calling into JS in response to these methods. So some people are experimenting with a slightly different architecture that would allow us to respond to them synchronously from the main thread, which seems really promising :)