Why is there any reason to suspect that those crashes would not have happen if the person was using platforms? Crashes are the result of a lot of variables, most notoriously the alertness of the rider(s) and their level of bike handling skills. Poor road conditions can also causes crashes. Also bear in mind that youtube videos usually are likely not a typical crash, or else it wouldn't be on youtube. People only upload extravagant or extreme stuff, because that's what gets views.