it’s a simple question of business model.
In the current model, the shadchan takes all the risk: the shadchan either gets the entire shadchanut, or nothing.
If you want the service provider to take all the risk, you invariably have to pay them more for taking the risk.
This is a popular business model used by many real estate agents, lawyers (who take contingency cases), farmers (who take the entire risk of crop failure), etc.
Many people in those businesses have adopted different models – fee for service OR risk-sharing. There are many real estate agents who work on a fee-for-service or hourly basis. There are farmers who will sell you a share of their crops (before the season begins).
For the most part the consumers cost for those services is lower with the second model, yet people are mostly unwilling to use that model. Here, we have a perfect case of that.
If shadchans were paid fee-for-services, you would probably pay them less. You could pay a subscription fee, then a certain amount for each service (date) they provide. If you don’t like the quality of their services take your business elsewhere.
Change is hard, but it’s not unreasonable to compensate someone for work done. you do that with your physician, right? The doctor gets paid whether or not the operation is a success.