Variety and diversity of the machines is something that might just re-kindle my interest that died away ages ago.
Oh to see 2 strokes v 4 strokes, singles, twins, threes, fours, sixes, eights. Flats, vees, inlines. Rotaries?
Different makes of tyre. Far fewer rules about how much fuel, weight restrictions, how much testing allowed, homologation, homogenisation, blah blah blah.
Won't happen again of course, but at least I lived to see those times.