The thing is, I agree with you - adding swear words isn't a panacea to make your talk instantly more engaging. Far from it! But neither do I think it's a lazy way out.

I'd be really surprised if any of my professional peers were offended if I were giving a talk and dropped in a swear word or two ... and I'd rather do so, and get a good reaction from a smaller percentage than water down my enthusiasm and reach nobody strongly.