The low-level retailer worker can change jobs much easier than a store can be opened/closed.
As such closing a few locations is absolutely trivial for Starbucks if it serves some larger purpose.
(Unionize all the stores in an area, and if Starbucks shuts them all down, just open a new coffee shop)
Furthermore, Starbucks shouldn't be forced to sell its proprietary assets. like ovens, espresso machines, technology, etc.
Most employees appreciate that they are getting paid whether or not the location performs well. They don't get an equal share of the profit, but they also don't pay an equal share to cover losses if the business is not profitable for a season. If a Starbucks locations were closed for a month during peak Covid, would the employees be happy to (a) not get paid, but also happy to (b) still help carry the cost of the lease, utilities and other operating expenses?
If I start a business and my employees are willing to put their name on the loan (backed by their homes as collateral), then this is a different discussion.
They are more common that one may think. They have quite a foothold in e.g. European agriculture and even finance https://en.wikipedia.org/wiki/Mondragon_Corporation.
Now go ask the bank for a credit line to do this and you will understand why the privatisation of money creation impedes worker-owned co-ops (or any ownership structure other than the standard capitalist one).
It is possible it is hard to find a co-op because it's harder to collect on a delinquent loan. Or perhaps data shows that they fail more frequently.
You argue elsewhere that changing jobs is easier than Starbucks closing all of their stores. The point is that this is one store, not all of them, and Starbucks can absolutely afford to close one or a few. They are betting that labor will back down before store closures start to hurt their business.