I don't care for strapless dresses much myself and if it was the style I was needing to wear, I'd look for a way to put in wide straps or sleeves. But this is simply me. For one thing, strapless looks like a fidgeting nightmare. I can't imagine being at an event, and moving around, dancing, etc., without having to hitch up the bodice or generally move it back in place many times over the course of wearing the garment. Although they can be really pretty, such as the green one Hilary Swank wore to the Oscars when she won her first award remains a fave celeb gown of mine.
As for the style to scream 'Let's Party!' as Miss Manners alludes to, and to be modest needs to have something on the shoulders, that's not exactly so. Of course strapless styles can show off more, though there are quite a few non-strapless ones that do as well and give off just as much as party vibe.