Only a personal opinion (and by no means an answer to the question) but whilst cycling (on the road) is a probably a fine sport in which to participate, as a spectator sport it must come a very close second only to golf as an utter bore. Standing by the side of a road halfway up a French mountain to watch a few dozen bikers and their assorted entourages wizz by in a few seconds (or a bit longer if you are on an uphill stretch) must be almost on par with watching two blokes trudge across a field (which 95% of golf consists of).
It can be sparked up all you like with different coloured jumpers, but the end result is a few seconds, or perhaps a minute or two depending on how strung out the field is, of bikes, cars (with bikes strapped to the roof), more bikes and motor bikes belt past. Sorry, not for me. It is obviously for the French as the impact of the Tour on the French economy is vast, with huge numbers of people taking time off to watch it.
In recent years this inexplicable mania has spread to the UK. Only this coming weekend the poor residents of Surrey and many other areas will once again be confined to barracks whilst some bike race or other wends its way from London and over Box Hill. There are plenty of cycle tracks where these events can be held and spectators can watch the entire event from the comfort of a seat. I especially like the race where one bloke dressed as a postman has the advantage of being on a moped. Eminently more sensible and far more entertaining than standing on a windy mountainside.