5.5? 5.6? Are you out of your mind?
A lot of hosting companies have to support a lot of older PHP websites and for that reason do not update. They have a good reason for that, because it breaks (or might break) many websites.
If CI requires newer (latest) versions of the framework, that would mean I can not create websites which can be hosted on multiple hosting providers (unless it is fully backwards compatible).
Not everybody has the luxury of being able to choose on which host (and so which PHP version) a website will run.
I have just seen the poll results and I really wonder in what world people are living? Please be realistic.