As Werner Vogels, CTO Amazon puts it "No Server is Easier to Manage than No Server" which in essence sums the move towards Server-less architecture.
Server-less architecture is the natural extension of reactive event driven design with Cloud infrastructure such as AWS. What it means is that servers or containers are spawned in response to events on the fly to execute a piece of code and then are shutdown with just a tiny bit of latency.
It has obviously lot of advantages such as:
- Very small and easy building blocks for complex applications of today
- They react to events and are on need basis.
- Low cost since one doesn't run the servers to execute code all the time, pay only for compute time.
- No maintenance.
How is it getting popular?
The likes of AWS is making it popular by providing on demand infrastructure at fraction of costs. One such service from AWS is AWS lambda(https://aws.amazon.com/lambda/). Basically IaaS and PaaS providers are making it easier to build such applications and architectures hence they are becoming extremely popular