This is where the concept of achazukei issur lo mechazkinan comes in. Why should a plain cup of coffee be a problem? Even the cRc’s recommended chumra was not on regular coffee, and only in certain types of stores.
There are people who don’t buy anything without hechsher, and there are things that could go wrong, but there’s no need to “be dan l’kaf z’chus” when it’s muttar meikar hadin.