I hear you - I don’t know why it’s never been in the main sink. I’ve just never seen it like that…

It’s not a separate sink, it’s a dual-chambered sink, it’s one big sink with a raised bit in the middle

The real reason for separate sink areas is that one is for un-dirtying them (this side has the disposal usually) and the other side for rinsing

Commercial sinks are usually 3-chambered (rinse, wash, sanitize)