This is too simplistic. There are varying levels of trust for myriad interactions.

You can trust someone to drive properly and not hit you.

You can trust someone to not rob you as you walk by them.

You can simultaneously not trust them enough to give them money if they ask for it without sufficient proof. Or not trust them enough to invite them into your home.

I think there's a problem with the way the word "trust" is used altogether. I trust certain people to drive badly, I trust them to forget appointments, and I trust them not to offer to pay the bill.

"Trust" being something defined as both exclusively positive and a virtue in the person that gives it is just meant to soften up marks, and is probably instilled into us by marketing and advertising. It's certainly not taught by any religion, who concentrate on being worthy of trust, not trusting.

You trust people because you know them well, and you know what they will do when confronted by certain situations because you have seen them react to similar situations before. Before you know them well, you're just operating from stereotypes and comparisons with other people you've known who have similar mannerisms. Or you're projecting your own thought processes into their heads. A "level" of trust is just a confidence level in a prediction.

If you don't have a friend who has had to sacrifice something for you, you don't know if you have any friends at all. That's the real reason it's hard to make friends as an adult. But after you've been through stuff with people, you'd be a fool not to know they'll come through in this new, far-less grave circumstance.

I honestly think the problem is that we're trying to make people fungible in a weird secular market religion, and they're not. Trust is not a credit score.