Yes, I’m sure the designers had some vague hand-wavy justification in mind, but the different weapon damages seem quite rightly there to serve game balance and give us options to puzzle over rather than to mirror real life. Some weapons are clearly better than others, but usually they’re then not available to all classes, or don’t have the thrown property, or some other factor that gives them a situational utility, or at least can do if you can find versions with magical effects.
I imagine the D&D designers spent a lot of time and effort carefully balancing the different weapons, which is why it mucks things up so badly when Larian do things like standardise range and get rid of the loading property, or let hand-crossbows be fired on a bonus action without a specific feat, so I very much hope this is going to be addressed in the final release.
Regarding slings, though, is it true that in 5e they can still be used with shields given they require ammunition and therefore a spare hand to load? I don’t know enough about 5e but from reading the rules that’s what it looks like. If so, I guess slings are pretty niche and only really useful to druids who don’t have proficiency in any other ranged weapon unless their race gives them one.
