“Going with coworkers” - Typically means going with predominantly coworkers with perhaps some plus ones showing up. So going without coworkers, at least in context, sounds much more like the decision to go alone than to find other, non-work-colleagues to go with.
Assuming the word choice was deliberate, which, no reason to not, if it were about coworkers vs not coworkers a more typical phrasing would have been “with friends from outside of work instead,” or even “with other people you know instead.”
It doesn’t have to be an assumption that those are the only two choices. Enumerating all choices wouldn’t be helpful, as there’s more than three.
Replacing group A with group B is less interesting, more obvious, and potentially not an option, or at least not an easy one. If it were, said lamented would likely be eating at a new restaurant with friends rather than lamenting. Or their friends aren’t brave and hate new restaurants, which functionally is the same as not having a group in that case. If they are all at McDonalds because “going to that little place on the side street that looks dingy and smells amazing” is scary, well…
Going out alone is less universally accepted, some find it weird, some find it uncomfortable. But a lot of us enjoy it. (Literally dozens of us). So sharing that idea will likely lead to more interesting conversation.