Respectfully, I think you're looking at this from a bad angle. You wouldn't go up to someone in the middle of a set, wearing headphones, and ask them to stop what they're doing to help you. Instead, you find someone who's finishing a set/exercise and politely say something like "hey, I'd like to try this exercise and you seem to know it well, would you mind taking a moment to give me a hand?".

I've personally done this twice this year (I genuinely wanted to learn, I'm not using it as a strategy) and it worked very well. I suppose culture plays a role but I'm in one of those countries where people don't usually socialize with strangers and it still works.

You need to find a better gym then...

"Hey man, can you spot me?" Is a pretty universal request, and frequently honored. Once you are done with your set, offer to spot them, and while you are both resting after your respective sets, start up some small talk. If small talk works, continue to bigger conversations.

Depends. I'm an introvert, but lifting is my second passion. I've noticed someone doing a lift I want to get better at and asked them for advice, form check, etc and they're usually excited to share the hobby. The reverse is true too.

: After astrophotography, before cycling

> However when someone is at the gym and another stranger asks them to stop and do a favor that takes time out of their gym visit it’s just annoying, not a friendship starter.

Might be the place you live; this is not my experience at all. I ask randos to spot me every week. People love to help out. Sometimes they'll even keep an eye on you in case you have another set and come offering.

Often I get asked to spot someone while their lift and I don’t mind, maybe you had bad luck.

Yeah, that sounds like really bad advice.

Personally I would read this as a weak, but noticeable signal of being a person who is okay with taking advantage of others. Most people are too embarrassed to ask complete strangers for actual favours.