For a lot of people, it's a practical issue. The risk of getting pwned by an entry node if you are an end user only visiting hidden services (ie, most people here) is relatively low, since it's never been demonstrated in the wild. The risk of LE finding incriminating evidence on your hard drive or of Windows malware infecting your computer and stealing your logins or other sensitive data are much higher, because we've seen both happen many times. Some people can't do full disk encryption for various reasons, so Tails is a good option. Plus, you can manually add bridges each time you boot, if you're really worried about it, and that's even better than monthly rotating entry guards.