That's a great question! I'll try and give my 2 cents:
I think there are different "tiers" that we can look at. There's a difference between running e.g. Spark using:
• Glue (Serverless)
• EMR (Managed Servers)
• EC2 + Apache Spark (just VMs)
• Bare metal + apache spark (traditional hosting)
Typically I'd go for the most managed approach (i.e. serverless in that case) when possible, and go to lower "tiers" only when that is required. This could be due to mee needing more flexibility and configuration, tighter security, lower cost, etc.
The beauty of pay-for-what-you-use services is that evaluating and introducing new technologies becomes so much easier. OSS tools have the added benefits of being able to consume them at different tiers without being coupled to a specific implementation.