On the one hand, because some brokers want to see a financing confirmation before they even do a viewing (so 10 people start looking for financing, although the property only exists once, resulting in 9 times the work for nothing...)
and on the other hand, many are still trying to secure old conditions (my DSL Bank branch sometimes received 300 more applications in one day than they usually get... in one day)
and also because many request 2-3 financings and then see where they get approval (because there is such a large deviation from price/value in the market).
So you could say that the banks probably do 50% of the work for nothing, but that drives up processing times... unfortunately...