The actual example I usually go for is selling/buying an apartment. I'm currently in Sweden, and I've gone through the process twice now. The contracts were several pages if clear text that even I, with my rudimentary knowledge of Swedish could understand. Good luck checking that everything is correct with a "smart contract" version.
I've also bought property in Sweden, it's very simple. No need to involve a lawyer even.
So where do smart contracts come in? Who would want to use a smart contract to buy an apartment? Unless possible the apartment deed was stored on the blockchain or something, but that is highly unlikely. Real estate is a very poor fit, since it's very heavily regulated in numerous ways. It's not just about ownership, and anonymous ownership of real estate is definitely a non-goal. It's an anti-goal.
I mean I'm not a smart contract evangelist, I'm just replying to your point that they are risky, that you need to understand them before using them. You do, that's why most people shouldn't.
As to use cases, you only proposed two things, coffee and real estate. Those examples are both silly, for different reasons. I think in general it very seldom would make sense to use smart contracts for real assets.
The only real use cases I can think of are financial derivatives with crypto assets as underlying, and various decision making mechanisms that govern processes that are controlled by code. As soon as you need to cross into the physical world, it's hard to see how it would work. Then you need a centralised institution that people trust, which mostly defeats the purpose.
When is the last time you needed to debug the contract when you buy coffee?