> They wouldn't dream of this with C, Java or even python (even though these probably work exactly like other languages they know -- unlike JS), but for some reason perfectly smart developers make this crazy decision all the time.
It's because they can. You can cobble something together and it works or seems to work. It may fail later down the chain but browsers accept all sorts of hackery, because they have been historically doing this for a long time. Before there was Javascript you could write broken HTML, nest elements wrong and browsers still figured out a way to deal with it. The expectations of half-assed solutions has always been there on the web.
It's because they can. You can cobble something together and it works or seems to work. It may fail later down the chain but browsers accept all sorts of hackery, because they have been historically doing this for a long time. Before there was Javascript you could write broken HTML, nest elements wrong and browsers still figured out a way to deal with it. The expectations of half-assed solutions has always been there on the web.