Why are backend developers supposed to know BE + FE + DevOps + Cloud whereas FE guys can get new jobs by just knowing FE alone.

I work on .NET stack primarily on Backend. Most job postings requires .NET + SQL Server + MongoDB / CosmosDB + Elastic search + Redis + RabbitMQ/Kafka+ Azure administration + Azure DevOps (CI/CD , Docker, K8, IAC) + Angular/ React. Whereas most job postings for Angular or React require just the knowledge of Angular or React alone. As per my knowledge the pay is kind of similar for a .NET full stack vs a React or Angular FE developer of same YOE. I live in a Tier 2/3 City and most companies are SBC's or Captive PBC's, that could be the reason. But still, ye bhedbhav kyu ?