Probably because some people became invested (financially and/or emotionally) in various strategies which were predicated on certain expectations of how Bitcoin would overcome it's rather obvious weaknesses and did not anticipate sidechains as being one of them.
In this respect sidechains are every bit as much of a 'disruptive technology' to Bitcoin as Bitcoin is to the mainstream debt-based monetary system. Naturally some people will lose, but they won't be going down without a fight.
I'm glad to see that we agree for once. It IS disruptive. And it will cause massive volatility whereby we all may lose as you obviously can't comprehend in your eagerness to criticize me out of spite. I'd love to see your face if and when you lose all your Sound Money BTC value to speculative SC's.
Bitcoin already has massive volatility in case you didn't notice (which is possible considering the number of 'Bitcoin up' posts you have made in 2014.) By the laws of nature we cannot all lose. Sidechains will, if anything, tend to act as a buffer to this volatility just as they will act as a buffer to coding accidents, legislative hassles, etc, etc.
I'd love to see the look on your face as you find yourself sitting on a pile of useless CorpGovCoins (formerly Bitcoin) when it turns out that they are as interesting to people as PayPal-II and some other solution has taken the place that Bitcoin could have occupied as a trusted and autonomous value foundation.