If I ask directions from someone, and get the right answer, and I'm not
wearing a seatbelt, I don't mind being told also "By the way, the cops around here are really strict about seatbelts; you might want to buckle up before you get a ticket".
Similarly, if I see code that declares all of its variables, I probably won't mention anything. But if it's obvious that adding "strict" reveals undeclared variables or other problems, it seems worthwhile to point it out, particularly if the user seems new or not particularly knowledgeable. If they know they can ignore it; otherwise, they'll learn eventually, and probably the hard way.
And thanks, I'd forgotten to check the weather before I left, and it is a bit chilly.