Why can’t the compiler infer @Sendable?

Evolution Discussion
1

this lives in Main.main:

try await s3.connect
{
    for asset:StaticAsset in StaticAsset.allCases
    {
        let content:[UInt8] = try assets.appending(asset.source).read()
        let path:String = asset.path(prepending: version)

        print("Uploading \(path)...")

        try await $0.put(content,
            using: .standard,
            path: path,
            type: asset.type)
    }
}

the strict concurrency mode doesn’t like this too much.

passing argument of non-sendable type 
'(AWS.S3Client.Connection) async throws -> ()' outside of 
main actor-isolated context may introduce data races
Main.swift(43, 9): a function type must be marked '@Sendable' 
to conform to 'Sendable'

the fix is straightforward enough:

{
    @Sendable (connection:AWS.S3Client.Connection) in
    ...

but this means we effectively can’t use the $0 shorthand syntax with async closures that take non-Sendable arguments.

why can’t the compiler just infer the missing @Sendable attribute?