Dispute arbitration does cost money, though (especially if banks would step in to make customers whole in case fraudsters are already out of their reach), which is why we're in this mess in the first place.
Other than that, Zelle has one huge advantage over the competition: The money is available in the recipient's bank account immediately. Venmo, Cash App etc. charge quite a bit of money for instant payouts.
Well, here's the problem: Zelle was never intended for this use case (i.e. B2C payments).
I believe they are planning to move into that space, but right now it's just the completely wrong tool for the task, and I've never seen it used for that myself (except for a few otherwise cash-only restaurants, food trucks etc).
Imagine having a concrete business and you bought Miatas instead of concrete mixers. Clearly Miatas are useless vehicles which serve no purpose seeing as how they can't keep a few tons of mixed concrete moving for an hour as it gets delivered.
Having a business set up to use Zelle, well, you're using the wrong tool for the job. We don't need every tool to be able to do every use case. Not every car needs to be a cement mixer.