Curious about why rice isn’t always included with Indian curries

I absolutely love Indian food, but I’ve noticed something interesting when ordering from restaurants, especially on apps like Grubhub. It’s not always clear if rice comes with a curry or if it needs to be ordered separately. Sometimes, leaving a note like “rice, please” works, and it gets included, but other times I’ve had to add it as a side.

I’m wondering if there’s a cultural or practical reason behind this? Is it just how Indian food is traditionally served, or is it more about how restaurants operate here? I’d really appreciate any insight from those who might know!