Maybe to try every solution they provide for free for a short time.
Droplets are not necessarily the main products sold by DO (or any similar companies). They provide DNS hosting, managed database instances, and even Kubernetes clusters. Yes, thereʼs a droplet under most of their services. But if you only get a droplet, you have to configure everything for yourself.
Thus, if iʼm about to evaluate DO for my company, Iʼd want to know if the software versions and configurations they provide are actually what we need. Maybe their Kubernetes is old as hell, or their MySQL instance doesnʼt support InnoDB. Little things i can only find out if i pay.
Sure, most cloud companies expect you to pay for the resources you use. I can fire up a Kubernetes cluster with all my components, connect it to a SQL database and run tests, and for this 2 hours iʼll only pay the price of a coffee, or even less. But Iʼd better drink that coffee instead.
Disclaimer: iʼm a paying customer of DO for years now. Also, i donʼt drink coffee.