Next "on" line please....

What's the deal with the people here saying "on" line instead of "in" line. I thought being "on" line meant being on the internet.... Obviously that's not all it means.
I first heard it at the grocery store (more about these so-called grocery stores later). The lady at the counter said "Next on line please, Next on line". I thought maybe I heard her wrong and then I heard another counter clerk saying the same thing.
Later that day - at Wendy's (yes - I know - we're in NYC - we shouldn't be eating at Wendy's).... the people behind the counter were saying (actually yelling) "next on line" too! Weird, huh?

Okay - now for "grocery stores". Tom Thumb it isn't. First of all - they are tiny, not condusive for strollers, and only one person (with or without a stroller) can fit in an aisle at a time. The selection is very limited and the brands/products they do carry are very random. Take for example - Cheetos. They have 4 or five things that look like Cheetos but aren't called Cheetos. Maybe there are tons of local brands here and that's what most people carry... I don't know. I'll have to get back to you on that one.
Anyway - we've been told by numerous people to use something called "Fresh Direct". They deliver groceries ($50 minimum) for a $5 charge. Sounds good to me - we plan to try it once we get our kitchen unpacked. For now - it's "eat out" or "take out"!