Why isn't SQS an event source for lambda?

On 28 JUN 2018 AWS Lambda Adds Amazon Simple Queue Service to Supported Event Sources.

Here is a good blog post that shows you how to setup SQS as an event source for Lambda in code. Example in Terraform:

# Event source from SQS
resource "aws_lambda_event_source_mapping" "event_source_mapping" {
  event_source_arn = "${var.terraform_queue_arn}"
  enabled          = true
  function_name    = "${aws_lambda_function.test_lambda.arn}"
  batch_size       = 1
}

https://medium.com/appetite-for-cloud-formation/setup-lambda-to-event-source-from-sqs-in-terraform-6187c5ac2df1