The popularity of hiring vendors for handling application backend has spiked tremendously over the last 5 years. On the one hand, startup owners go serverless to save infrastructure costs and pay for resources as they go. As the company scales, relying on third-party vendors allows getting access to backend resources as quickly as possible.
Although implementing cloud-based infrastructures is mainly popular among startup owners, large-scale companies use distributed architectures as well. Amazon Polly, for one, fully relies on AWS for project support.