Welcome, oldgit. If I read you right, the 'straps' you mention may be top tube protectors (against the handlebars swinging round to hit the top tube). Spokecards started as race numbers in urban races and they're now used outside of that context, e.g. as souvenirs of a ride. Some people like looking at them on theirs and other bikes to perhaps discover what, if anything, they may have in common with another rider, or just what they've been up to.
Welcome, oldgit. If I read you right, the 'straps' you mention may be top tube protectors (against the handlebars swinging round to hit the top tube). Spokecards started as race numbers in urban races and they're now used outside of that context, e.g. as souvenirs of a ride. Some people like looking at them on theirs and other bikes to perhaps discover what, if anything, they may have in common with another rider, or just what they've been up to.