I stumbled accross an API that is using IFrame to communicate with an underlying third party system. I wondered ok is this just an old system, I noticed the system exposes besides the IFrame a well structured relativly modern REST API. Which made me wonder. Are there any specific advantages for them to use an IFrame instead of REST API ? The exposed functionality through IFrame is Product selection and price retrieval. If there was not an alternative set of REST apis I would have just thought that this is something very old, but now it looks to me as an **intentional choice**.

What may motivate such choice in 2021?