If you want to send something to a computer in school or a work PC or something without admin rights.
snapdrop / sharedrop work in browser, without any installation, and that’s the point. As much as I hate web apps, sometimes they are your only option.
I agree that localsend is great when you need to exchange files between your devices often, but when you quickly need to send a file to someone’s PC without admin rights, snapdrop and sharedrop are a faster way to achieve that.