Accessibility level of interface and its members

[Wit-2k]

Default accessibility level of an interface is "internal", while interface members are "public" by default. Why?
If I want to implement current interface outside, isn't it that I have to declare this interface with modifier "public"?

[HaloFour]

The default accessibility of all types is internal. The default accessibility of members is private, but since an interface describes a contract, interface members must be publicly accessible. Other accessibility levels weren't supported until C# 8.0 with default interface implementation.

[Wit-2k]

Seems C# is designed to be this way. I accept and thanks.