> I don't entirely understand why they "didn't want to touch it"?

Customer: it’s just this specific solder job

“They”: that’s what you say, but there might be other issues, and we cannot tell without spending lots of time checking things

Customer: no, it’s just a solder job.

“They”: OK, we’ll solder that, but the risk is on you, and you’ll pay regardless of the outcome.

Some time later:

“They”: operation succeeded, patient still dead.

What do you think happens next?

A: customer thanks “them” for their effort, pays and leaves

B: customer starts bickering that “they” destroyed their phone, leaves negative reviews online, etc.

I expect a significant percentage for option B. Even if that’s rare, it requires only a few negative reviews to not be worth it.

I can see people wanting to avoid that, even if it effectively leaves money on the table.