Because Google knows best. One size fits all.
Also because Google is concerned with possibly malicious extensions.
When you open Chrome, you might see this:
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As usual, an article in gHacks will explain to you what to do to remedy this. There are a few things you can do, however there might be cases where the solution might not work, unfortunately.
Source:
http://www.ghacks.net/2014/05/28/unsupported-extensions-disabled-re-enable-blocked-extensions-chrome/?_m=3n%2e0038%2e1258%2ehj0ao01hy5%2e1azu