We use it because we are already running our own k8s clusters in our datacenters, and we have large storage requirements for tools that have native S3 integration, and running our own minio clusters in the same datacenter as the tools that generate and consume that data is a lot faster and cheaper than using S3.

For example, we were running a 20 node k8s cluster for our Cortex (distributed Prometheus) install, monitoring about 30k servers around the world, and it was generating a bit over a TB of data a day. It was a lot more cost effective and performant to create a minio cluster for that data than to use S3.

Also, you can get durability with minio with multi cluster replication.