When an account is locked on Twitter you're asked to verify your account using your phone number. This phone number verification may be available to some, but it excludes many users who do not have a phone number or who can't afford a mainstream phone provider. If you don't have a provider that Twitter supports, you simply get an "unsupported number" message and no other options to unlock your account.

Twitter does allow appeals to be filed, however they are very rarely looked over and responded to. The app uses emails for password resets and other similar things, so it makes zero sense why email confirmation can't be provided as an alternative to phone number confirmation in these cases.