On backpressure block

After watching Ben's great JavaOne 2014 talk, I was wondering why there isn't a onBackpressureBlock, i.e., a strategy which blocks the producer thread. 

On one hand, I can accept we don't want to encourage blocking operations, on the other hand, this operator may allow casual Observable.create() implementations to not worry about backpressure at the expense of blocking one Schedulers.io() thread.