It wouldn't surprise me if this subject-dropping was introduced into English by non-native speakers? English is actually a bit peculiar as languages go in its wanting to put a subject in practically every sentence. It's raining. It's about time. What is the "it" here referring to? Linguists will tell you you're looking at a subject placeholder that doesn't convey any special meaning but simply completes the grammar. And people learning English from other languages that don't need this fail to see the point. So they just start saying "About time we dropped that stupid it!" and then even native speakers start thinking yeah, why not ditch the subject if we don't really need it?
It's a thing that happens in most languages that create rules about sentence structure.
Basically, really important or frequently used statements will break the rules to... Save time.
Can you imagine that scene from scene from half bake, instead of "Fuck you, fuck you, fuck you, fuck you, you're cool, fuck you, I'm out!"
You'd get "I will fuck you, I will fuck you, I will fuck you, I will fuck you, I think that you are cool, I will fuck you, I will leave now."
Something like 'Im going to the store' only becomes 'going to the store!' in contexts of urgency and familiarity, like yelling it on the way out the door to your spouse. You wouldn't likely do that in your workplace.
Yeah, one context in which a subject is not required even with proper English grammar is in imperatives, which makes sense given the implied urgency. If "Watch out!" had to be something more long-winded like "You must watch out!" you'd probably be dead.
The top two are not too far out, the Spanish is similar - "you I love" "see us". Be right back is so weird in English but funnier in Spanish, ya vuelvo, sounds like "I am already back"