No, not if you’re a mature, responsible adult.
1) Not everyone is “a mature, responsible adult.” Precaustions are needed because some are not as mature. 2) Even “a mature, responsible adult” cannot trust himself on issues of inter-gender interactions, without precautions.
Not only do I say “Good Shabbos” to people I see in the street, I also say “Good morning” and “Good evening” to the bus drivers I see every day when I get on/off the bus. Never once has it resulted in a wink, a shmooze or a “full-blown relationship.”
You rarely if ever see the same bus driver on your morning route again. The threat is somewhat lessened as a result. Someone you see regularly, you need greater precautions.