The initial interaction is the point for that, not just never speaking to any one. If they politely or brusquely brush you off, it's harassment if you continue. Not for the initial interaction.

There's also loads of non-verbal cues which guide you to who's open to talking to or not. I don't talk to random people much, but I do get asked for directions all the time, even though I'm a 6'2 guy. I think mainly because I'll happily make eye contact and smile at random people who look as if they're a bit confused or lost. I deliver the non-verbal cue that I'm happy to help if they want it. That triggers people in need to ask for help.

If someone struggles picking up on those cues, it might be worth practising at places where people are supposed to be meeting other people. Meetups, networking events, etc.