Non-lawyer here. Someone I know who IS a lawyer says that the maxim "Expressio Unius Est Exclusio Alterius" governs conduct everywhere, even in non-legal settings. I asked if it governs the conduct of teenage boys trying to date my teenage daughter. He said that absolutely it does, and that ignorance of the law is no excuse. Frankly, I have no idea what he's talking about. What would it even mean for this maxim that he called a "canon of construction" even to apply here?
Your lawyer friend is misguided
Casual conversation and writing are not subject to any maxims of interpretation - the words mean what the speaker/writer says and what the listener/reader understands and these may be different things.
In a conversation about restaurants, there is no implication that the places not mentioned are not restaurants or don't exist. Even if I were to write a published magazine article called "The 10 best restaurants in the world", there is no implication that no other restaurant can possibly be better than those 10.
This applies even in business settings. For example, this is the Petbarn logo:
It has images of dogs, fish, cats, and birds. By your friend's argument, it would be unlawful for them to sell products for the care of pet snakes or lizards since they aren't on the sign? Or, for that matter, to operate from a building that is not a "barn"?
Finally, your friend is wrong even in legal interpretation. There are many ways of contract and legislative interpretation that are or have been in use in every jurisdiction.
"Expressio Unius Est Exclusio Alterius" is one maxim of interpretation but it may be in conflict with others. For example, if a regulation on aircraft listed various types of aircraft but didn't mention helicopters but nevertheless had an entire section devoted to rotor maintenance the "Rule against surplusage" would require that helicopters be included.
In any event, modern courts tend to take a more holistic view to interpretation and the use of individual maxims is optional.
"Expressio Unius Est Exclusio Alterius" is the Latin version of a general rule of communicative interpretation to the effect that when people give a list of things, the list is presumed to be complete (the more detailed the list, the stronger the presumption). This is not a hard and fast rule anywhere, but it is harder and faster in the context of rules (game, bylaws, law) than elsewhere. For instance, if a host names a choice of 4 kinds of desert, you should assume that is a complete list (therefore don't ask for banana pie if that's not on the list). In non-rule contexts, a list might not be exhaustive so there might be some statement like "We have all sorts of choices" that says "This is not a complete list". Laws use certain expressions like "including but not limited to" that has the same effect. In the context of law, because the stakes are higher than in ordinary voluntary social interaction, the maxim is more strictly enforced.