The benefit you're suggesting, that all the restaurant's transactions would be on the blockchain and so lenders could automatically evaluate the risk, is at odds with my understanding that bitcoin has high transaction costs and slow speeds and it is therefore unlikely that all of a restaurant's patrons would ever be paying with on-chain transactions. Maybe they could pay with something like a Coinbase credit card, and Coinbase could make transaction histories available to lenders - but I have to imagine something like that exists in current finance with our current credit card companies.
Just because code makes the decisions doesn't mean that there is no bias and discrimination built into the code. This will eventually create bigger problems down the road due to the massive scale this can be deployed at when compared to a banker having to make the final call.
These are the problems being worked on in defi right now and why people are so excited about it.
> in the cryptocurrency future, how will it be easier for a restaurant to use their business as collateral to take cash to do upgrades?
In the idealized future, the restaurant would have their complete transaction history available on-chain for lending contracts to use. Then, instead of a banker making a decision if the restaurant deserves the loan, an algorithm can make that determination and instantly grant the loan. Such a contract might use data points like amount of restaurant supplies purchased, number of customers, average sale price, demographics of the location, all of which would be on-chain and available to a contract.
This is good because it removes bias and discrimination that currently exists in the traditional system, increases the speed at which your restaurant owner can access their capital, and decreases the overall cost of doing the transaction because humans don't need to be involved.