In particular the hosting credits really lets you play around with dev without breaking the bank.
In most cases startups utilize AWS and GCP and they are generally really good, but both DO's Hatch and IBM a lot of people are missing out.
DO is awesome for startups without really good devops since they streamline a lot of the config work so it helps a lot getting the basics set up. We have a lot our free user plans on DO because it's much more cost effective and predictable (pricing wise) than AWS and GC.
IBM is also useful in a different use case because of their easy to setup dedicated hardware servers. 10k per month buys a lot of dedicated hardware (esp GPU) if you need it which is a godsend for us since we do a lot of ML and performance is dramatically better than any of the g/p instances on AWS.