Its a fine line between suggesting and preaching. Nobody likes to be preached to unless they are already in the fold to some degree.
Back when I owned an actual brick and mortar type record store I did more than my fair share spreading the word. It was the right venue for it... Its not hard to get a guy buying a copy of Meaty Beaty Big and Bouncy to go for a Fleshtones or Chesterfield Kings record. Pretty much that guidance is what they're there for.
Opportunities like that are fewer and farther between nowadays. I mostly wait until someone asks my opinion.