The purpose of source cache context is to tell a source where and for how long to cache certain files.

Restore ensures that the caching is shared across the whole operation through https://github.com/NuGet/NuGet.Client/blob/dev/src/NuGet.Core/NuGet.Commands/RestoreCommand/RestoreCommandProviders.cs#L86.

Unfortunately that pattern is not applied everywhere.

This leads to needless allocations and could potentially make things more difficult should we want to change the cache time.